I played it, and here's my opinion on it:
As far as movie-liscensed VG's go, it's not terrible, but it's not great either. As far as video games in general go, it sucks fairly hard.
For the most part, the levels are very monotonous. Wolverine's levels are all pretty much the same thing happening over and over again. Nightcrawler's missions manage to add a tiny bit of variety, but are still pretty boring. Iceman's levels are just completely out of wack. Iceman's flying controls just feel really out of place in this game, for some reason.
The characters' levels are not broken apart very evenly at all. The reason this is a bad thing is because it means that Iceman might end up going through almost half the game without being able to fight and level up, and then suddenly have to a face a big boss fight just out of nowhere.
I really wish they would've at least given your allies some degree of good A.I. For some reason, both Storm and Colossus appear to be total idiots. Storm cant do crap unless you tell her to by clicking in the left control stick(on the xbox version). Colossus is apparently unable to handle a group of 3 unarmed human soldiers on his own without you there to help him.
The only thing that might've been able to save this game, would've been co-op multiplayer. Unfortunately, co-op would'nt really have made sense with Iceman's gameplay, and it might've gotten to cluttered and confusing with Nightcrawler's gameplay, but I think Wolverine's levels would've been quite fun with some co-op action.
Personally, I'd really rather not get started on the graphics or the cinematic cutscenes. Those kinda speak for themselves.
Anyway, if you wanna grade this game among other movie-to-game adaptations, then I'll have to give X-Men: The Official Game a 5/10. However, if you wanna grade it as a general game among games, then X-Men: The Official Game deserves a disappointing 3.5/10.
(p.s. Squall, for the Nightcrawler vs. Multiple Man fight, one of the things you need to remember is to teleport onto one of the light poles and heal every now and then when you need to. If you get on top of the light pole on the opposite side of the arena that you're already at, then you should have a good amount of time to heal before Multiple Man has time to get over there, multiply, and start shooting at you.)