The game looks fun, and a SSB-esque game with a Playstation cast is pretty appealing. The thing I don't like is that only super moves can kill, and they're an instant kill if they touch you. Not only that, but doesn't that make it insanely hard to balance? After all, a majority of a character's worth is going to come down to how powerful their supers are (or rather ease of use vs how many kills can be acquired in one use) because all their regular moves are just for show (yes, for building meter, but they do absolutely nothing beyond that)
Even if they do manage to balance it, I feel like it might get stale rather fast. I fear it will boil down to "Mash standard attacks to get meter, when full press the super button next to someone for a point."
The thing that makes SSB so entertaining is it's extremely dynamic. Every character has a set of moves that have different damage and power rates, plus the character's themselves have different weight's etc. You might land an extremely good blow on someone, but they'll just barely manage to make their way back to the stage, whereas you land the same blow on a different character and they won't have a chance. With All Stars, it doesn't matter who you're facing off against, if you touch them with a super move they're gone.
I'm not saying SSB is more balanced or anything (let's not get into that :/) but it's that dynamic "You never know exactly what's going to happen" factor that gives the game its re-playability and makes it so interesting. So far, All Stars severely lacks that from what I can tell, and I can't say for certain it will get stale, but it'll really have to hit a sweet spot with the way the game mechanics are set up.