I rented it yesterday and played it for about eight straight hours with some friends of mine, getting to the fourth Act out of five, and I can definitely say that this is just as fun as the first one, if not even better. There are new playable mutants, like Bishop, Juggernaut, Magneto and
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Deadpool (Yes! Haven't unlocked him yet, though apparently he has the Wisecrack as a boost ability).
Some of them are pretty ineffectual, like Sunfire, even if there is some irony in the lone Japanese member of the team raining atomic destruction on his foes. Seriously, his Xtreme special is a giant mushroom cloud.
All the item drops are random now, so there's a very Dark Alliance feel to killing things and picking up equipment like The Emitting X-Armor. Unfortunately, there are level requirements for equipping items. Thus, a lot of the stuff that you pick up isn't usable until ten levels later, which can be frustrating since you end up carrying all these great pieces of armor that you can't use. At least you can store the items you don't need in the Hero Stash at your HQ. Another cool thing about the HQ is that now you can redistribute all your skill points for a mere 10k at Forge's - so if you end up preferring one skill over another but sank a lot of points into the latter skill, you can take all the points out and put them into your preferred one instead.
I think that the nicest little tweak was the addition of the Auto Level Up. You toggle whether you want the characters who aren't being player-controlled to equip new items and spend their stat/skill points the very second they can, without having to flip into the menu to screw with their stats every level up and bore the hell out of everyone else who's playing. Also, they finally fixed it so that in the hub areas, everyone can walk around and do things instead of only one character, which was totally excruciating in XM:L if you weren't player 1.
If there are any downsides to it, the game seems like it's going to be completed in a rental - if one day of thorough playing gets us to act four we're probably going to have finished it in two or three days, though there is an unlockable hard mode and some secrets to get. Also, the opportunity for screwing other players over is lacking compared to the first game - I have fond memories of swooping down from the sky as Storm and throwing Wolverine into the electrified water pits in the old Ship level. But overall, this game is pretty spectacular as a rental. If you and some friends want to finally play something other than Halo 2 deathmatches, I highly recommend X-Men Legends II.
On a final note, the most unintentionally hilarious thing in the game can be seen right from the start. As Magneto, just face up and walk slowly. He gives new meaning to the word 'sass'.