Please, Kobe isn't an elite one-on-one defender either. Kobe can play good perimeter defense, but is better used as a roamer. Kobe wasn't the one guarding Kevin Durant and Paul Pierce in crunch-time during the playoffs.
Wade's superior athleticism and timing make him the better defender. I believe he's been the leading SG in blocks the last two season. Plus, he can easily get you 2+ steals per game and led a strong defensive team last season starting marginal defenders in Rafer Alston, Carlos Arroyo (at different points), and Quentin Richardson.
Kobe was the best player on the best team, but not the best player in the league on an average or very good team. He didn't elevate the play of anyone on that team. The list is pretty good with some questionable placements in the middle.