In cube we have access to all the very best mana ramp. This makes it pretty hard for green two drop ramp to get all that much of a look in what with there being sufficient one mana options available. There has to be some fairly significant extras on offer with the two drop options to temp you away from a cheaper alternative. The main advantage you can look to get from a two mana ramp card in green over a one mana card is getting a land into play. Lands are safer than creatures, they trigger landfall, and they empower plenty of things. There is lots in the way of good reasons to be wanting that slower safer land in play than a flimsy fleeting dork but here we are looking exclusively at creatures that cost two mana. We are bypassing the land or dork debate on an individual card basis and just looking at what it takes for a dork to be good enough to cost a whole mana more.
We are also going to just look at green creatures. Yes, Vedalken Engineer is a powerful card but it is pretty narrow and not something that is useful to compare here. The stricter one keeps the parameters for cards to compare the more meaningful those comparisons can be. For this reason I will also be taking out Sakura Tribe Elder from the discussion as it sits directly between a creature ramp spell and a land ramp spell. It is certainly a great card and would sit near the top of this list but it isn't functioning in a similar enough way to be usefully discussed here. Gold ramp cards can compare but are broadly just too narrow to be worth playing in drafting cubes. There are none so much better than a mono green one that you should bother constraining draft options to include.
Other powerful cards failed to make the list for being too polar and thus not improving the way your cube will play. Sanctum Weaver, Bloom Tender, and Priest of Titania can all be pretty insane mana dorks that provide massive returns for little upfront cost. The issue is that you need support to do that and that in turn means your card is either underwhelming or pretty unfair good. That doesn't lead to good games and so we are far better off looking for more rounded cards and have nice high floors instead of stupid ceilings.
You could argue Lotus Cobra falls down for being too polar, which is certainly a criticism of the card. If it lives and you have a sac land and get to not only have two mana of any colour out of it but also get to do free damage or crew with it or whatever it all seems pretty unfair. I think Lotus Cobra fell down more as removal started getting better and more common. There are simply too many effects that kill a one toughness creature with absolute ease. Your chances of winning the game of magic drop an astronomically large amount when your Lotus Cobra dies to the soft end of an Arc Trail etc. You take that risk with a one drop but you simply don't need to with two drops and so for the most part you will find staying power to be a big feature of two drop mana dorks in general. This is certainly where Deathcap Cultivator fails to have any allure in cube.
One might ask why we are bothering to play dorks at all when there is a wealth of two mana land ramp, and even Talisman and Signets on offer at the two slot? If safety is such a big deal why would we bother with these fragile mana dorks at all? Tempo and utility and value are the various answers! Cube is a very rounded format and it is fought hard with both tempo and value in most games and matchups. A late game Rampant Growth does very little while a creature might provide that much needed blocker. An unused land cannot apply pressure while a mana dork usually can. Mana dorks can be useful in the early and mid game outside of their primary role as a mana dork and they can avoid being dead in the late game. There are of course all the many things that scale with dorks from equipment to Anthems to vehicles and all those cards that find dorks or let you play them from the top of your deck. Some decks just really want a high creature count to scale with their various other cards.
It is in part for these reasons that we do not see Wall of Roots getting much love in cubes any more despite clearly being a premium mana dork. It is very bad at crewing or holding equipment or pressuring opponents stuff. Walls/defenders in general have seen a steep decline in use in cube since Kaladesh era and the arrival of vehicles. It is not something specific to ramping defenders although they were some of the more commonly seen types of these card in cube.
So what else nearly made this list but failed? Gyre Sage is one such card, it has a nice ceiling and can produce lots of mana while enjoying some cool synergies. Problem? It can do nothing and floor is more important than ceiling, especially on a role filler card like a ramp effect. Reclusive Taxidermist is the other end of that spectrum. The floor is fine but what it offers you back in ceiling just isn't much of a draw. Just some vanilla stats and even then, only maybe.
Lastly there are Gala Greeters and Prosperous Innkeeper, and arguably even Nest Invader, who are a bit Gilded Goose, a bit Sakura Tribe Elder and even a bit Lotus Cobra. They are like Goose in that they do not assure ongoing ramp. They are like Tribe Elder as they can be pretty hard to prevent from providing a ramp. And they are like Cobra as they can attack and ramp at the same time! Greeters are an interesting utility card but as ramp they are far too slow and unreliable. They cannot ramp you to four mana on turn 3 by themselves and that is pretty much enough to kill their chances in this list. They can also be a do nothing 1/1 which is a problem for any card looking to have a home in cube! I like them most as a threat with cool utility. Innkeeper on the other hand just isn't enough card. Life is whatever and 1/1 body isn't impressing anyone. Equally Invader is just some stats and of less value than coloured or ongoing mana production by quite a margin.
Sylvan Caryatid 8th
Much as walls are not where you want to be, three toughness and hexproof very much is! This is as close to a land in terms of reliability and safety as you are likely to get from a creature. It survives most removal, and critically survives almost all removal that would stop this from ramping to four mana on turn three. It also blocks very well and provides far better colour fixing than any land ramp is providing. The utility of being able to soak up damage or provide mana all with relative safety is outstanding. This card is comfortably cube power level and one of the best ramp dorks that the ramp decks on the slower side of things can use. This is only not in my cube due to there being so many good options at present and the meta tending towards proactive decks. If things swing back the other way this could easily get back in.
Incubation Druid 7th
The floor on this is low but at least reliable. A little tougher than most one drop dorks and a hint of fixing. Where this one excels is with ceiling and synergy. If you manage to get a counter on this quickly and at low cost then you are going to be wildly ahead on mana and likely win from that alone. A bit like when you manage to successfully level up and keep alive a Joraga Treespeaker but better! Pretty easily one of the best ceilings for a card on this list but it requires support from other cards which makes it a bit polar and narrow. Luckily the adapt mode gives a much easier to reach pseudo-ceiling that makes this a relevant body, a mana sink, and a much bigger ramp spell. It is a royal pain trying to attack into four untapped lands and an Incubation druid as it can block, become a 3/5, munch an attacker and then untap with at least seven mana and a much improved board state. This means that even without synergy this is one of the best late game dorks on this list. Great card, lots of fun, but sadly, when it comes to ramp you want the bulk of the card to be performing well on turn two, not in the late game.
Devoted Druid 6th
Similar floor to Incubation Druid that then trades all that late game ceiling for the ability to produce an extra mana one time. Sounds like trading a lot for a little but it is trading a lot of stuff that isn't part of why you are playing a card, and that you will be getting from other cards, for something you are directly playing the card for. It is a bit like how both Lightening Helix and Bolt are both better than a Searing Spear but Bolt is directly better and so is the much better card overall. Incubation Druid likely has the greater sum of parts but Devoted Druid is just better at ramping. It is the only two mana ramp card that reliably gets you to five mana on turn three without help or support from other cards. That can be utterly back breaking for the opponent. Indeed it is why I have shied away from this card a little over the years. Easily powerful enough for cube but a little polarizing. It forces people to build and play around it as they can so easily just lose to some hard hitting five drop wildly ahead of schedule. Even an Acidic Slime can be good games if it is coming down and destroying half your lands in play! Think what what a five mana Nissa might feel like at that pace! There are also cute synergies with buffs that let you milk extra mana out of Druid, even infinite mana, although those are not all that great in cube. I have even seen this used as a means to prevent a Jitte from charging which is quite cute.
Tangled Florahedron // Tangled Vale 5th
Comfortably the lowest power card on this list. Just an overcost Llanowar Elf stuck on the back of a bad forest. I have just been really impressed with the play of this card. It does what you want it to and it provides a lot of dynamic options. You can play conservatively with it as a land or aggressively as a dork. You might do this to avoid removal or because you have too many or too few lands in hand. There is a tricky art with playing ramp as you don't want to wind up with too many mana sources in your list as you then start flooding too much and folding to answer heavy lists. Equally there is no point playing ramp and cutting lands as missing land drops entirely negates the benefit of ramp. This little card does a great job of keeping your land and ramp balance in check. It is card quality for ramp decks. Usually you are just trying to get a good balance of land and spells but ramp decks need to mix ramp in to that equation as well and this is a handy little tool to help out with that.
Llanowar Loamspeaker 4th
Relatively early days on this one but so far it has been impressive. The body is sizeable making it fairly robust in the face of removal. An OK blocker and fine ramp and fixing. Getting all those important floors raised to a healthy point. And the sweetener? We can start throwing lands into the mix as 3/3 dorks. This is better than it sounds. Early it is a strong disincentive to deploying planeswalkers and late it is somewhat of a persistent attacker. You are typically able to chump attack with excess lands making this a more robust threat than a mere 3/3 would be. It is not a super powerful ability but it is direct and broadly useful. And given that it is on a perfectly acceptable two drop already doing the job you want from it perfectly well the card seems rather good.
Exact same palatable floor as the Loamspeaker but with a much more immediate and oppressive upside. Dorks coming in bigger is going to get out of hand fairly fast. Green is dork heavy and so it will be fairly consistent in triggering this and getting ongoing free value. Even on the dorks that don't scale with being made bigger this counter is worth the best part of a mana. Once you are casting cards like Walking Ballista Biophagus is effectively tapping for 3! This card should be higher on this list and I have marked it down for two fairly biased and likely inappropriate reasons. Firstly it is probably just too good for heads up cube play. It is designed for commander where this sort of early tempo doesn't snowball and is far less powerful. Secondly, it is a 40K card which means it isn't going to be for everyone.
Paradise Druid 2nd
This is my favourite of the cards on this list from a design perspective. It hits the mark perfectly on power level without being at all polar or narrow. All the power it has is located in the right place. The card has no silly late game tag ons, it is just a reliable two drop mana dork that fixes, is able to get into combat, and stays nice and safe in the lead up to such things. Much as this is a contained card it does also scale nicely with some things, notably getting vigilance, and holding equipment. Getting your dork killed in response to paying an equip cost can be such a devastating tempo loss that it cascades into an actual loss. Paradise Druid is one of the best cards in cube to play with equipment. The increased frequency of the ward mechanic is doing some good work diluting Paradise Druids impressiveness on that front but that is no threat to the cards cube spot as we are all about the ability to ramp first and foremost. This very reliably ramps and then it has some other perks as a pleasant side effect of that reliability. The upsides here are exactly when a two mana ramp card can be worth playing over a one mana option.
Roffellos, Llanowar Emissary 1st
A classically terrible card design. This is narrow because it has a GG cost and because you need to play it with forests. It is also vulnerable thanks to a mere 1 toughness. These all make it less powerful certainly but they are not a good way to try and offset extreme power. They just make it horribly polar. Oh, I can't kill your Rofellos, I guess you will have twice the mana for the rest of the game then? Nissa Who Shakes the World is pretty oppressive and she is a five drop. Roffellos is absolutely the most powerful two mana ramp dork to the point where I "banned" him out of my cube. He just isn't what you could call a good magic card that leads to good games. If your cube is all about extreme power and having fun doing rare and cool shit, as a nice alternative to playing some drier formats like standard or modern then I am all on board with packing this guy. If however you are looking to have the best and fairest possible games and the most options in draft and deck building then this is not the kind of card you should be looking to run in your cube.