2) voldemort
3) snape

after that, you have a bunch of candidates: bella, mcconagall, kingsley shacklebolt, hermione, and, by the looks of it, molly "john mcclain" weasley.

and maaaaybe harry. yes, he took down voldemort, but that may have been like the mavs/warriors, where a better team got took down because the lesser team was completely designed to exploit their flaws. we already saw snape whup up pretty decisively on harry. all the wizards listed above clearly know more spells than harry.

on harry's side, though, he did fight bella to a draw when he was 15, even if she probably would have won by split decision on the judges' scorecards. he also took down every other Death Eater he faced in the series. he also seems to have the whole higher magic thing licked, and he's obviously got balls of steal.

if you're just talking in terms of dueling, i would think 17 year old harry could probably beat anybody but dumbledore, snape, and mcconagall. so, by that standard, i guess i have him at #5.