well as much as I hate MUA2 due to the fact that it has less playable characters,shorter length,less costumes(not to mention that most of the alternate costumes are infamous and ugly),less powers and no RPG elements, I'd still say that MUA2 is generally better than its prequel.
Why? the game has changed so much especially with the graphics and environment, the levels are very well designed especially the early levels of the game and they reminds me of XML1 which feels a bit like a platformer whereas since XML2 onwards the game them feels like a boring dungeon crawler,it's like you're visiting the same flat caves and factories again and again...
in the previous games you only face generic objects again and again to be thrown and destroyed, but here there are a lot of varieties (even though none of them can be wielded as a melee weapon unlike in MUA1),some of them are really fun to play with, for example Jean's Phoenix Fury will demolecularize and lift objects and one of Storm's powers can clear the way.
The powers are far more interesting to use despite the limited number (except a few characters who has been turned into absolute crap by VV,I'm pointing at Mr Fantastic,Venom and Daredevil...they were some of the most fun characters in MUA1 but now they're the complete opposite...Cap and Human Torch remain almost unchanged) and they evolve at higher level like XML1's powers.
Combat is much better than MUA1 where you can't chain from a 3hit move into powers. Now the chain move feature from XML games is back.The combat from XML2 to MUA1 was a stepback,replacing strong attacks with a chargeable knockback move is never a good idea
The basic fighting moves are also a lot better, where it was the weakest point of MUA1. Now some characters such as Gambit and Deadpool really use their weapons during attacks, who would want a basic sword slash move and staff assault as powers?
I'd give the game a 8.5...If I had the DLC and there is a gold edition with more DLC (why the heck is the X-Men without their leader in the next-gen versions?) and additional maps, I'd rate it higher than 9...still hoping for them to bring the DLC back