OP, what fights have not been made that the fans want to see? (Excluding fighters who were not signed to the UFC)
The only fights I want to see that don't look like they'll be happening are all surrounding Nick Diaz. I almost died at the though of the Anderson Silva fight (which I still think should happen) and the fight with GSP (which was understandable because the UFC won't let the fighters rule the roost).
Everyone has little fights they would like to see, but the superfights that can be made are in the process.
Anderson Silva Vs GSP is the biggest fight ever for MMA, and it's looking like it will be made without too much effort. I personally don't think Jones Vs Silva is a relevent fight to make (Does a prime 24 year old really deserve to snatch the legacy of an aging Silva?).
Fights people want to see:-
GSP Vs Silva - In the works.
Silva Vs Jones - Will probably never happen.
JDS Vs Overeem - Should be in the works next year. Was arranged with unforseeable circumstances.
JDS Vs Jones - If Jones continues to dominate, moves up, and earns his place, it will happen.
Aldo Vs Edgar - Arranged.
Diaz Vs GSP - Was arranged with unforseeable circumstances. Diaz has to earn his place.
The UFC has not really just let anything slide without it being taken care of. Jones and Silva is the only fight that can't really happen. Jones and JDS might never happen but that's just because it's so far away. Anything not including Fedor or out of the UFC guys has been taken care of and addressed, some with mishaps along the way.
This is excluding all the great non superfights that have been put together.
If you're a real fan, you don't see one or two bad things happen in a row and suddenly turn on the entire sport. The UFC is maybe the best run organization in ALL OF SPORTS. Stfu and be glad that you're getting to enjoy such an exciting sport in the prime of it's existance.