Comics Alliance did a "100 Greatest X-Men" poll that wrapped up a few weeks ago. Their panel of five judges rated the characters on 1-10, and their scores added up to half the total. Everyone else could vote, and we made up the other half. I did vote, but only once on each character, though I considered stuffing the ballot box for Stacy X. But this blog does not support electoral fraud!
I didn't always understand the rationales behind how their panel was voting. Some characters were getting credit for actions on various X-Forces or Excaliburs, but Strong Guy, for example, who get knocked for most of his best stuff happening with X-Factor. Mystique got high scores despite all the panelists lauding her work as an X-Man villain, which seems like it should result in low scores for being a great X-Man. It's almost like the whole thing was a silly and completely subjective fun exercise!
Really, my biggest issue was their panel was 80% Cyclops fans, which is some Olympic ice skating levels of slanted judging.
Also, someone actually described Jean Grey as "the heart and soul of the X-Men," which, ha, no
To that end, I thought I'd argue Deadpool's case for Greatest X-Man. He has an extremely limited resume, partiallu because the X-Men are jerks who won't let him on the team (even though they welcome people like Magneto, and Namor, and Mystique, and Gambit. Freaking creepy scumbag Gambit!) However, the few things he's done could be argued to have an unexpectedly large effect.
Point #1: When Hope was born, as the first mutant since House of M, Cable rescued her from not only a bunch of racist Purifiers, but also Mr. Sinister. But he wouldn't have managed it without Deadpool's help. Now, however you feel about Hope, or Avengers vs. X-Men (I'm not particularly a fan of either), Hope was pretty instrumental in making it so there could actually be more mutants. If only anyone had bothered to ask those folks if they wanted to be mutants. . .
The fact this was also hamstrung within what, three years?, by this Terrigen Mist nonsense is not Deadpool's fault.
Point #2: Evan Sabahnur, possibly to become Apocalypse in the future. Or maybe not. I know Fantomex set him up to be raised initially in a more peaceful environment to try and stave that off, but from what I can tell, Wade is the one playing the (bizarre) older brother supporting Evan's efforts to avoid that fate. Probably because Wade knows a little something about people trying to make you into something they want, rather than what you want. Also about how it can be easy, but ultimately suck, to play into others' low expectations for you (basically, don't start acting like a world conqueror, or a buffoon, just because everyone thinks that's what you are or will be).
If Evan does avoid becoming Apocalypse, I'm going to credit Deadpool as one of the major positive influences. When Evan got inverted during AXIS, became Apocalypse, and rampaged, it was Wade who tried to talk him down (and got torn up pretty badly, even by his standards). And Wade who found a place for him to hide after he reverted to his usual self, with everyone now freaking out about Apocalypse. And Wade kept urging him not to take this as some sign he was destined to become Apocalypse.
So, might have helped block the return of a serious X-foe, and helped keep the possible jumpstarter of the mutant line out of the hands of one of their other serious foes. I think that's a pretty solid couple of things to hang one's hat on. And it doesn't even include the time he gave the X-Men a serious PR boost by pretending to be a dangerous lunatic who thought he was an X-Man, allowing them to save the jerkass father of one of their students from Wade (see Daniel Way's Deadpool run). Or all the help he gave Cable during his "show the world a better way" phase, even when Cable would act like a dick and treat Wade like a chess piece to manipulate.
So yeah, limited resume, but it's a good one. Like, "solved cold fusion", and "found Grand Unified Theory". OK, fine, maybe it's more like, "built coffee pot that turns on automatically when your alarm clock goes off", and "women's jeans with practical pockets". Although I've been told that last one would be pretty popular. Point is, he's doing more with less.