I prefer the quiz type shows where you can shout the answers at the tv. I quite like the ones with no real money at stake, like the Einstein Factor, where people answer questions on whatever subject they're interested in (anything from physics to Xena Warrior Princess).
I usually prefer general knowledge game shows. I used to like Who Wants to be a Millionaire?, but would rarely choose to watch it these days. Current game shows I sometimes enjoy are Pointless and The Million Pound Drop. I also like The Eggheads.