X-Men Legends is a competent, squad-based hack-n-slash.
X-Men Legends is a competent, if not especially deep, action-RPG. The gameplay follows pretty similar to the vein of Diablo where you take your crew into an area filled with bad guys, beat the crap out of said bad guys, and level up your powers. There's a pretty interesting story to the game, and the inclusion of playable classic X-men stories, like "Night of the Sentinels" or Juggernaut's break-in at the X-Mansion. The graphics do what they need to do, but are never intended to be all that great. This game is fun, even if it's a little repetitive.
This game plays sort of like Diablo or Baldur's Gate:Dark Alliance, where you barge into areas filled with enemies, tear them apart using standard attack combos and unique abilities, and then finish off a boss. The real difference here is that you move in a squad of four instead of solo. A pretty quick tap on the d-pad changes who you control, and you will need to change quite a bit. The controls are pretty tight, and there are a number of combos that you can do to your opponents. You'll quickly find that the mutant power combos are indespensible, as they deal out a ton of damage. The melee attacks follow a set number of combos that will knock your enemy back, juggle him, or trip him up.
Some characters are naturally more useful, while others are pretty much useless (*cough* Beast). The characters all follow a similar pattern. You can build 2 attack powers, like claw slashes or optic blasts, 1 "buff" like Iceman's ice armor, and 1 "Xtreme" power with which you'll unleash hell on any onscreen enemies. Also, you get a number of stat increasing abilities like more HP, mana, and augmenting your attacks with your abilities, like Iceman adding cold damage to his attacks.
They used cell shading and low detail to provide a comic book feel. It does what it needs to do, but I'd hardly call it inspired. The soundtrack is ok, and does a nice thing where it'll play a nice ambient background until an enemy shows up. Once faced with danger, the sound maintains the same theme, but picks up into action mode.
As you go through the game, you'll run into 3 types of unlockables. First, you find sketch books that unlock concept art for the game. Meh. Also, you'll find comic books that permanently increase the stats of your X-Men. Naturally they are very useful. Lastly, you'll get CDs that unlock Danger Room missions. The Danger Room missions are generally pretty cool, and get nice and tough by the end. I especially like the character challenges as you get to unload a case of ass whooping using your favorite character. By far, the coolest unlockable was reliving a few missions from classic X-Men books. It's cool to see your characters in their old 70's gear battling against squads of Sentinels.