When I bought this game I expected it to be crap so my expectations were low to begin with. I consider this a game that would have been somewhat acceptable if it came out during the early original XBOX age (2002). The only reason I got the game was to finally see why Nightcrawler wasn't in the X-MEN Last Stand movie.
As for the gameplay its really not that hard except for the battle between Wolverine and Sabertooth. That took me like seven tries before I figured out how to finish Sabertooth off at the very end.
My suggestion to all is to play the entire game on the Hero level this way you get accustomed to the controls for each character and the game won't get totally frustrating. You can then go back and replay the levels that need to be completed on Superhero mode with you characters already leveled up.
I actually started a new session file playing every mission only on Superhero mode and was able to complete the game. I never would have been able to do this if I hadn't gotten accustomed to the controls.