great for a first attempt!
...but there's still a lot of glaring flaws. the engine in general is just too damn fast - if anything, you should try nailing the engine and THEN build your characters around it.
As a side note, some of the sprites felt a bit mismatched in a way - you had Sonic and Knuckles' modern sprites yet Mario had some sort of weird fan-made thing.
also, I personally think it could do without the silly fan characters (blade and that other sonic guy)