For the most part I loathe reality shows, but I do like certain types of them
I'd divide them into categories as follows...
Talent / Skill competitions - Dancing with the Stars, Top Chef, Project Runway, America's next top model, etc. I admit, I rather like Project Runway - its cool to see all the designs (I otherwise pretty much ignore fashion) and the stresses the competitors go through etc. I also sort of like America's Next Top Model. I sort of got into Dancing With the Stars a little bit this last season, mostly because I was curious to see who would win but I think some people get WAY to into it - I mean, I was curious to see who wins, some people I know seem concerned and caring about who will win, as if it will somehow matter in their lives.
Social / Elimination games - , Big Brother, Survivor, etc. - really find these shows to have no redeeming value - its all scheming, alliances, etc. Couldn't care less.
Shows that exist to feature a celebrity - The Kardashians, Hulk Hogan's show, Paris Hilton's show, The Osbornes, etc. I really don't understand society's (or some segments of society's) fascination with celebrities and their lives. Nor can I understand what the appeal of these shows is - to me they feature mostly contrived situations.
Ditto pretty much for these shows that throw a bunch of unknown people into a house (MTV's Real World, Jersey Shore, etc.) and just watch them interact through a bunch of situations which to me seem mostly contrived. Or similar shows that just follow the lives of a bunch of non-celebrity, random people (The Real Housewives of Orange County / Beverly Hills / Atlanta etc.).
Amazing Race - I'm not sure which category this fits in but I find this show pretty interesting even though in some ways it doesn't quite live up to its own premise - its hard to be a true race when there are checkpoints at the end of each episode that essentially pause the race and allow everyone to catch up (more or less), instead of it being a continuous race.