Right now Bisping and Diego are the best fighters but Griffin has better accomplishments and in the long run will have the better career.
Bisping hasn't even had his first fight in the UFC yet besides the TUF 3 finale. Griffin has beat some tough opponents. Jeff Monson, Elvis Siniosic, etc.. Some of the decisions he's lost were controversial. When he fought Dan Severn that was controversial decision. When he fought Tito Ortiz, that was a controversial decision. in my opinion, Griffin has fought the toughest opponents out of all of them, and fared really well against them. Diego has beat some tough guys, but he still has more to prove. Griffin proved he can hang with the big boys. As for Evans, well, he needs to become more of a Mixed Martial artist. Rashad has done nothing but win judges points by making it a wrestling match. The judges are mediocre and he just gets slams and just wrestles with his opponents the entire match. If he wrestled with Matt Hammill, Hammer would beat him. Rashad is an excellent wrestler but he needs to become a mixed martial artist. Forrest needs to improve on his strength. He needs to start bulking a little and become stronger. He also needs to become more of a smarter, pin-point striker rather than a brawler. He is very tough, really-well conditioned and has a huge heart. Diego has great submissions and is a good wrestler but needs to improve striking and face tougher opponents. Mike Bisping needs to fight someone
Btw, why aren't Mike Swick, Kenny Florian, or Chris Leben on this list? I know none of them won, but Leben almost had a title match and Florian and Swick are close to title matches.