I was really surprised with who I ended up maining.
Mario got nerfed as far as his down+b goes, and I just can't use him anymore.
Captain Falcon just isn't the same, he's a bit slower and weaker. And due to the changes in brawl, a constant series of raptor boosts isn't possible anymore.
I still ended up maining olimar though, along with pit and pokemon trainer.
Olimar just seems to work for me, I've memorized his moves and I just know how to use him.
I've developed a few strategies for pokemon trainer, switching between ivysaur (to rack up damage) and charizard (to finish it off). I don't see much use for squirtle, though.
As for pit, his recovery is amazing, and he can rack up damage and finish fairly well.