Good, but not as good as the original.
In the original, each character had multiple costumes and powers to unlock. In this one, there are only two costumes, with only aesthetic differences, and only 4 abilities (each mapped to one of the face buttons). While this does make the game a lot simpler, it gets rid of the depth that the original had. Also, there are many portions in the story where a particular hero is made unselectable. While it makes sense for the story, if it is the hero you wanted to play as, you just have to deal with playing someone else.
The game has received a graphical update and the audio is a little less annoying. It still can be a little troublesome keeping track of yourself on screen, especially once you have 4 human players, but overall, the presentation is improved. The dialog has also been adapted for a morality system, though choices have little or no affect on the outcome.
If you've already completed the first game and want some more, then Ultimate Alliance 2 will somewhat deliver. On its own merit, its a fun cooperative game. However, the original outdoes this title and would be more worthwhile if you've never tried either.