I hate "competition-style" reality shows and talent contest shows and avoid them like the plague.
I also am not a fan of "confessional" type shows where the cameras show stuff happening and then a participant rants into the camera about their roommate or someone.
The ones I enjoy watching are:
Deadliest Catch: I thought following the lives of crab fishermen in Alaska would be dull viewing. I was wrong. I've decided not to watch this season, though, because it's too sad to view one of the main "stars" knowing he died before production of the latest season ended.
Gene Simmons Family Jewels: It might be debatable how much "reality" there is in this show (I've had my doubts), but as an improvised sitcom, it's great and better than the Osbournes, IMO.
Dirty Jobs: If they could build a movie around the Crocodile Hunter, they can get Mike Rowe to do a comedy film about some of the jobs he's had to undertake.
Mythbusters: Well this one goes without saying. I can watch this one over and over, and not just for Kari Byron.
Ice Road Truckers: Same as with Deadliest Catch, I thought a show about guys driving up and down lonely highways would be dull, but it isn't. I recently found out the show is produced by the same guy who produced the 1996 Doctor Who movie.
Murder in Small Town X: The exception to my hatred of competition-based reality shows. This was a short-lived Fox game from 2001 in which contestants were taken to a town in the US Northeast (Vermont, I think) which has been partially populated by improvisational actors, who enact a Twin Peaks-style mystery story as the contestants try to solve the mystery before they are "killed off" by the villain. I wish they'd put this on DVD but they won't because the winner was a New York City fireman who died on 9/11 -- one week after the finale of Small Town X aired.
Joe Schmo - And of course I can't forget one of the best parody series I've ever seen. I prefer the second season over the first.
Alex