X-Factor is pretty lame. The problem with it is that it can cover up for bad play, in a game already in which 2-3 mistakes can literally cost you the game already, X-Factor just simply makes it more overboard ridiculous in these terms. I've never seen another Marvel vs Game in which there were so many 1v2 or 1v3 comebacks ever. Prior to this during MvC2 you would see epic things like Justin Wong's 1-pixel comeback or his solo Cyclops win over Yipes Team MSP, fact is, during MvC2 it took 100x more effort to make a comeback within a similar situation, especially when down to only one character, and X-Factor greatly increases these odds, as witness to what we have seen numerous times even at the highest levels of play. I don't believe UMvC3 is a great game at all, due to the fact it feels more TvC then an actual Marvel vs game (making a button a launcher ).
However I don't despise those who play it, because its your taste. Not only that but at Evo, it was easily the most hyped Finals and Grand Finals at the tournament other then KoF XIII (while AE:2012 Grand Finals was kinda meh).
Lastly, broken games are played a lot, and can be downright fun. Like GG didn't have any dumb bs, or 3rd Strike didn't have Chun/Yun winning 98% of the tournaments or that Tekken Tag wasn't full of Mishimas and Ogres during its prime. The gameplay is what will draw and cater players to wanting to play, and without a doubt hype for the game as well. Balance is overrated.