
There are a lot of unlockables on the PSP version: arcade versions of some of the games, a lot of interviews, and a cheat sheet if you play all the games in the collection. Each has different requirments to unlock like the 1000 coins in Alex Kid. The console version does this too, it just has more games.
I can't imagine that huge game being put on the Vita. I'd love to see it in action though. I wonder how it plays.