They very wildly depending on the type.
Group 1: Game-driven competition shows where one person/team gets eliminated each week - Massive Freedom Shows (Survivor and The Mole (early 2000s reference there) are the two best unscripted shows ever made)
Group 2: Single-week competition shows- Fun to watch, but I won't go out of my way to not miss a week
Group 3: Talent-driven competition shows (i.e. any singing/dancing show- cooking shows are kind of a hybrid of Group 1 and Group 3)- They're fine, but not exactly my cup of tea all the time
Group 4: Melodramatic MTV-type reality shows, usually without any sort of competition- Awful, and usually fake (legally, a show only has to be real if there is a prize)
I generally agree with this. I'll add...
Group 5: same group of people over and over buying, selling and/or fixing sh**t-if I like the people it's fine, if not, unbearable.