Really, you have to break "reality shows" into categories. Because there's different types of shows (and shows are often a hybrid).
1) Drama Shows - Shows that exist just for the drama (Real Life, Real Housewives of [insert city])
2) Competition Shows - And, of course, this gets broken down further:
2a) Game Shows - You can't argue that these aren't "reality" shows (Wheel of Fortune, Jeopardy, Deal or No Deal)
2b) Creation Competitions - Competing to have the best of something (Chopped, Face Off, Forge in Fire)
2c) Goal-Oriented Competitions - Trying to be the first to complete something (Amazing Race)
2d) "Other" Competitions - Mixture of types, or no set "goal" or purpose, just staying in the competition (Survivor)
3) Job-Based Shows - Shows that feature people doing their jobs (and/or hobbies), and/or behind the scenes of their jobs (Undercover Boss, Judge Judy, American Chopper)
4) "Other" - Shows that don't really fit into any molds (Mythbusters)
The problem seems to be, that anything that's not a pure game show (stuff falling solidly into 2a) has a tendency to fall toward Drama. Big Brother exists specifically straddling the line between Drama and Competition. And while some drama is acceptable, it needs to be in moderation (and not scripted/edited in).
Remove the drama, and most of the time shows are fine. I mean, heck, other than a certain person, Heroes of Cosplay (which I'd categorize as a "Job-Based Show") would have been fine, if it had just been about the creation of costumes and what it's like to compete. But they had to fill it with drama (and a certain person), which ruined it.