You get to beat people up while you pretend to be a super hero. That about sums it up.
The plot is broken up into 3 acts. In the first act everyone is friends with each other. The 2nd act breaks the playable characters into 2 groups: those for the registration act, and those that oppose it. You get to choose which side you want to fight for, which will also dictate which playable heroes will be available. In the 3rd act, everyone becomes friends again, more or less, and the roster of heroes to pick from increases.
I should make mention that I've only played the side of the anti-registration group so far.
There is a decent selection of characters to pick from, whether you do the bonus missions or not, however I stuck to a small roster. Once I got a solid team of heroes, I never bothered to trade them in for anybody else.
For each mission of the main story line, you will have a team of 4 people available, which you can switch between on the fly.
There are lots of powers to choose from for each character, all of which are upgradeable, including a variety of passive powers. Passive powers are ones that are activate all the time, and will often consist of improving ones overall strength or stamina. You can upgrade skills using cash found along way as, or with points that are gained as you level-up. You level-up by gaining experience, which you get by defeating enemies. If you change your mind about which powers you've leveled up, you can redistribute your skill points later on.
You're team-mates also gain experience and level-up even when it's the CPU controlling them, and they do so at a decent rate so they're able to keep up with you. Even heroes you've left on the bench for half of the game will level-up. This makes it easier if you decide that you want to try someone else out, as you won't be stuck with a level 1 hero trying to fight off the tougher bad guys that appear later on.
The characters and variety of super powers in the game helps add to the constant battling you'll be doing. Since there's not a lot of differences between the enemies you'll face along the way, it helps from making the plentiful amount of combat get too boring, although you are likely to experience some deja-vu throughout the game, given the similarities between the stages themselves. The mission goals are often different, but how you achieve them remains the same: beat people up and break stuff. And unfortunately that's the biggest flaw in the game for me. Despite all the characters, and powers, and things that should make the game exciting, the uninspired levels and the repetitive nature of the action just makes it 'okay'.
To provide a breather from the action every now and then, you'll come across the odd simplistic switch puzzle and the occasional computer terminal hacking mini-game. A few more puzzles would have been welcomed by me however, to add a little more depth to the game-play.
In addition to the main one-and-a-half campaigns, there are also bonus missions which will allow you to recruit new heroes, and even villains, to your side. To recruit the characters, and unlock them for play in the main campaign you'll have to reach certain goals in the mission. The bonus missions have the added benefit of letting you simultaneously earn skill points and experience by completing them. If even more combat isn't your thing, you'll also get access to trivia games you can play for added experience points.
A set-back with the game that I've seen a number of players get upset about is the quality of the graphics. They are definitely not the best the PS2 has to offer, but at the same time they weren't a bother to me. I could tell what everything was suppose to be, and they were functional. That's all I really need, but it's not hard to see that this is one area that was not focused on. The character models are block-y, and the environments are fairly dull.
The controls are a little backwards compared to most other action titles. I'm used to seeing X being jump, O being grab, and square and triangle being weak and strong attacks. For this title, triangle is jump, square is grab, and X and O are your attacks. Although this felt confusing at first, it really didn't take long to adjust.
Melee combos are pretty simple to pull off, as are your special mutant power attacks. You can also do team moves with a few quick buttons presses, in which yourself and one other member in your party will perform a heavy damage attack. For example, Psylock can pull nearby enemies close together while Blade jumps overhead and starts shooting at them, or Spider-man will make mace-like weapons as he swings around pieces of rumble.
Between the 1.5 story lines to play out, the number of character combinations available, and the bonus missions to beat, super hero fans may find a decent amount of replay value. For myself, the repetitive nature of the action hasn't won me over to go through and start another play through just yet.