Bisping might be better than some of the guys that have gotten title shots (Buentello, Eilers, Hardy, Hominick, Abbott, Leites) but the issue is greatest fighter to never win a title, you have to fight for the title and Bisping didn't and won't ever do that. Thiago Alves earned his title shot and did so by defeated top ten guys. Lytle, Hughes, Kos, and Karo is a pretty amazing run and personally I would even rank a Chris Lytle or Karo Parisyan over a Michael Bisping.
As for Kenny Florian, the kid earned his three title shots and he's likely going in the Hall of Fame. Bisping had three chances to earn three title fights and he failed each time while Florian had four chances to earn title fights and he won three of them.
I too would put Kenny above Bisping for that reason. Plus Kenny was a finisher. Tough to be that good at finishing at 155. That said, Kenny doesn't really have 1 career defining win. His best win of his career may be Guida or Joe Daddy. Not that Bisping has many if any career defining wins.