Whitebeard is pretty strong right now as he's appeared and is finally living upto his reputation. His victory over Usopp could either be due to his current bad assery being fresh in the minds of people, Strawhat avoiding or Usopp having won a tournament already(does he really need to win two?). The Usopp fanbase was pretty big(and rightly so), but I really don't see Whitebeard overcoming the Zoro fanbase if Bon Chan couldn't.
Buggy has a fan following, but I doubt it's strong enough to win against the remaining contestants…maybe Nami/Roger, Enel, Brook/Garp(although I can't see him besting Croc) and at a reaaaaaaaaaaaal push(and some awesome campaigns) maybe Sanji. He maaaaaay make it through the next round, but it's doubtful.
Croc, on the other hand seemingly has one of the largest fan followings on Arlong Park, probably larger than most the members of the strawhats. He doesn't do much for me, but I can see him winning his match.
I'm finding it hard to see Enel progressing much further to be honest. His fanbase doesn't appear to be on par with some of the other non-strawhats, but maybe I'm jumping to conclusions.