TUF has produced big fighters from almost every season. Think of Nate. He's only JUST got himself a title shot. Current TUF guys are having decent little steaks all over. TUF isn't really about seeing the next world champion, it's making an MMA TV show. It gets people into MMA (as it did with me when I watched UK Vs US). What brings it from a decent TUF to a great TUF is the coaches. Does anyone care about Carwin/Nelson? Cruz/Faber? Everyone liked Wanderlei/Vitor and Bisping/Mayhem. When they are interesting characters, it makes for a good season. The added bonus is stockpiling a new group of potential prospects into the UFC and giving them great training experience and a small fanbase beforehand.
I'm probably the best at keeping threads on topic of all time.