X-Men 2 in my opinion was lousy, compared to XMen1. I loved and still love XMen1 much more. Graphically XM2 was better, if that's something you care about (I don't). XM1 was/is one of the best adventure/platformer games, by far. The level design I thought was pretty stellar, since there is no 'one way' to get through each level. The helper X-Men was pretty cool, too. XM2 was more of the 'find the switch, run as fast as you can' type. The most important thing was every character was completely different, with different strengths and weaknesses, which sometimes necessitated switching, whereas XM2 reflected nothing of the sort. Also, X-Men 1 focused a great deal more on teamwork in 2 player than XM2 did.
XM-2 was on okay game. It made for some fun, but you can't really compare it to XM-1.