Pretty fun, if a little repetitive.
User Rating: 7.5 | Marvel: Ultimate Alliance X360
Basically, your typical button-mashing action-rpg, similar to baldur's gate type games. The more stuff you kill the better powers you get, etc. However, unlike most action rpg's I have played, this one has some measure of replay value. At a certain point, you basically have to decide on a 'team' that you will more or less stick with, and straying from it is not wise because you will end up facing higher difficulties with less able characters. I myself am not much of a comic book fan, never have been, so don't buy into the 'its only fun if you're a comic nerd' type of reviews that seem to be out there. Comic fan or not, it's interesting to see what leveling up Thor will do vs. what Moon Knight or Wolverine will do. That said, many of the powers, while particular to the individual character, are different only visually. For example, plenty of characters have a power that hurts enemies in a close area around the character, as well as a ranged power. The results are pretty much identical, but the visual effects accompanything them are different. In a way this trivializes your choice in characters, but also provides variety, something lacking in most action rpg's. Also, you can find alternate costumes, and have to get to certain points or accomplish certain objectives to unlock certain characters, so you might not get to play your favorite character right away.
Another strong point in favor of the game is the settings are varied and interesting, from underwater to an asian-themed temple, to a castle. While you will fight many of the same thing over and over again until you get to an end boss (a downside typical to action RPG's), it gives you enough bad guys to try out your different powers on.
Overall, this will be good entertainment for just about any action video game fan, but if you're not a big xmen fan, it's probably better for you to just rent it. I rented it and it was fun for the 5 days I had it, but not being a die-hard xmen or comic fan, i probably wouldn't have messed with it much more than a couple of more days. 
