Rashad is the easy number 1. Having Diaz and Brown over Griffin is a travesty. Serra is also a high mention, but giving the unusual nature of Season 4, it's hard to say where he should end up.
If we look at it from a numbers game, Rashad, Forrest, and Serra became champs. Diaz, Florian, Dodson, Koscheck, Cote and Sanchez all fought for the belt, and Dillashaw is on his way. Gastelum shows a lot of promise, but I won't bite until he beats a guy in the top 10. Bisping, Big Country, and Brown have done well for themselves, but have yet to win against a top 10 fighter either. Bonnar gets a slight reference as honorable mention.
So if I had to make a list, it would be 1. Rashad, 2. Forrest, 3. Serra, with 4-10 some mix of the other mentioned fighters outside of Bonnar/Cote/Gastelum/Brown. Bisping gets the nod over Brown in my book based solely on strength of schedule, even though he lost all of his bigger fights. Also, Serra could drop to 4 and switch with maybe Florian, Koscheck, or Sanchez.
If I missed a TUF fighter/winner who fits into the above categories, I apologize.