Generally speaking, I much prefer scripted TV shows. I like it when I find characters that I adore and that I can relate to, even though they're fictional characters. I find that reality shows often just make me depressed about humanity! I think it's mostly because, like you say, reality TV is like a train wreck or a car wreck - the networks put people on reality TV shows that they know people will watch, usually out of the same sense of voyeuristic horror that we look at car wrecks.
There are two reality TV shows that I love, though - So You Think You Can Dance and Project Runway. I don't love all competition shows (American Idol, for instance) because I think the whole "America voting" can be annoying, and it is more about popularity than true talent. I generally like the way judging is handled on SYTYCD, where a mixture of the audience's votes and the judges' opinions goes into deciding who gets sent home each week (though sometimes this backfires, like it did with the first 2 episodes of duets from this season's SYTYCD [U.S. season 8]). And Project Runway is just hilarious because of the "characters" on the show - I think Heidi Klum is a riot, and I ADORE Tim Gunn - I wish he was my fairy godmother or something like that!
The reality TV shows that just follow people around Real World-style (Kardashians, Jersey Shore, etc) just leave a bad taste in my mouth. I'm sure if I started watching them I'd get as addicted to them as the next person, though, which is why I try to stay clear!