Of course it's not Smash Bros... but that's not a bad thing.
Where All-Stars really shines, and somewhat faulters, is the kill system. You gain AP by attacking opponents and once you reach level 1, 2, or 3 on the AP bar you unleash a special attack with R2. AP can be reduced with certain items and with throws but it's inevitable that at some point a special attack is coming. It's quite interesting how tense the game gets trying to dodge or stop people from unleashing their specials, though once you get to level 2 or 3 they are damn near impossible to avoid. Overall the system works and can provide very tense gameplay, but it can also be immensely frustrating and cheap at times. I'd also like to point out that while the environment can kill you, those deaths don't actually count which is rather odd.
As an entire package, All-Stars is a pretty good game. It's a lot of fun and is a blast to play with a group of friends. A few design choices could've been better, but overall you won't want to miss out on All-Stars.