This game is definitely several steps down from the first. The computer player is unchallenging, and Namco decided to compensate for this by making you do all sorts of ridiculously boring missions in order to unlock all the hidden players. Instead of giving you a challenging computer opponent, they come up with all these ridiculous rules to make the missions "harder". But these don't actually test your skills in the game... they only test your patience. How much time are you willing to waste?
The graphics are good, but even if you're buying this game so you can play against your friends, you're going to end up wasting your money. You'll only be able to play with a few characters. All the other characters have to be unlocked by playing their stupid mission mode.
There are other problems with the game, too. The music sucks, for example. Also, your characters will be slow to respond to your commands, especially blocking. Don't even think about trying to block in this game (much less guard impact!), because it will never work, the interface is just too slow.
The only solid improvement in this game is the graphics. As a game, though, it's a big let-down and a big waste of time. Stick with SC 1.