I was a huge fan of the Ultimate Fighter at one point. I missed out on TUF1, unfortunately, but watched TUF 2-6 religiously. I'd have to say that TUF 2 and 4 were my favorite seasons.
There was something cool about having a team of tried and true veterans looking to make a comeback on TUF4 that resonated with me.
When Rampage faced Forrest in TUF 7, I started to notice my interest in the show wane. I'm not sure exactly what it had to do with. This was the first season that the fighters squared off before the show even started. I guess that component may have not been as intriguing as I suspected it would be. There seemed to be less talent from that point toward, with the Heavyweight season the exception.
I watched again during that season, but after that, it became less and less interesting.
I usually feel way less inclined to watch when there are seasons with fighters below 185. There often ends up being a lot of petty squabbling and Napoleon complex issues in the house, and it makes me wish the days of professionals like TUF4 guys were back. Sure, there were some goofballs like Shonie Carter and Mikey Burnett, but everyone was pretty respectful and didn't feel the need to act like petulant children.
I'm just trying to pinpoint exactly what has made my interest wane. Is is the coaches? The format? The night? Lack of talent? Lack of finishing power in lighter weights? Or all of the above? 
It's just stale at this point, and there really aren't many (or any in some seasons) true prospects. The drama is boring and lately the fights are even worse. I've been watching The Smashes online, though. That's a bit more enjoyable.
depends on the coaches for me
I will watch a season if i like the coaches...the season on now sucks
No group of fighters or coaches made me stop watching... Putting it on Friday nights made me stop. Your main market is 18-34 males.... Yet you put it on a night where almost no one in that age group is gonna be inside watching tv? I understand what they were trying to do, but it failed dismally
no matter who the coaches are the fights are always shit
I haven't mever stopped I watch at least an episode of each season except for the most recent
I enjoyed GSPvsKos more then a few seasons before that, got bored of lesnar vs jds, i really liked Mayhem vs Bisping(one of my favourite seasons) TufLive sucked, brazil was ok, havent bothered keeping up with carwin/nelson but have been watching smashes.
I think it's because every other season is lightweights and welterweights. The season with the featherweights was and bantamweights was quite good
I haven't quit. I am the eternal optimist and keep hoping it will get better.
I liked tuf 5 the best. Stoppes watching during the middle of last season 
I have never missed an episode of TUF but this season is so fucking horrible I really am not sure if I will watch another episode until next season
i really hate that guy with the red mohawk.. looks like hes throwing another bitch fit in the next episode
Last year i liked it only because the fights were live. This year the fights are boring (no finishes yet) then crap decisions and pink mohawk d-bag who can't get a job and makes his pregnant girlfriend work 2 jobs just so he can go to the gym make it even worse. Hell you know it's bad when you put him getting mad about someone farting onto the show
TUF 10 was when I started to really lose interest, it was so fucking gimmicky. Bringing Kimbo on and then we find out later Kurt angle was going to be on. The Rampage/Rashad "beef" throughout the season. Fights sucked half the time because they gassed. Although we got some legit fighters at least.
11 with tito/chuck, garbage.
12, eh it was bearable
13 was awful, just awful
14, good
15, live format was good
16, couldn't get through the first episode
Junie browning?
KZTT_FawkingxD - Junie browning?
Exactly what I was thinking. It was that season I was like wtf am I watching. That whole cast sucked pretty much
GriffinQ -No group of fighters or coaches made me stop watching... Putting it on Friday nights made me stop. Your main market is 18-34 males.... Yet you put it on a night where almost no one in that age group is gonna be inside watching tv? I understand what they were trying to do, but it failed dismally
This. If it has to be on Fri, they should at least move it to 8, so their target demo could catch it before they get ready to go out.
TUF starting going downhill when they eliminated the challenges, and made the fights 2 rounds.
I also disagree with their letting fighters stay in the "main house" after they lost; the old-school TUFs had a feel to them reminiscent of Agatha Christie's Ten Little Indians.
the tuf comback season was the best one.. after that i didn't watch much
I watch them all I don't give a shit