right now it's:-
s1 - Forrest - won show early 2005 and won title in mid 2008
s2 - Rashad - won show late 2005 and won title in late 2008
s4 - Serra - won show late 2006 and won title early 2007
s14 - Dillashaw - finals of TUF late 2011 and won title early 2014
plenty of title contenders to go along with it: Florian, Sanchez, Koscheck, Diaz, Maynard, Matt Brown, Bader, Dodson
most of the guys are journeymen and gate keepers, plenty are cans. But as far as picking good fighters, they do a decent job, w/ more emphasis on personalities than top prospects the last few years - it is a reality tv show after all.