When I was a kid, I thought they were quite convincing. 
when i was a kid the only reality tv we had was cops (i consider this the first reality show ever). growing up poor and with broadcast tv the only form of entertainment at hand, and cops was on all the ****ing time, and that was reality tv. they didnt edit for drama they didnt play the individuals against each other. they just followed cops around and recorded it and with very little editing (aside from trimming the boring parts, getting arrested is usually a long and drawn out process), aired it. then came the sensationalized season long game shows, which became the standard for the reality tv for awhile. i didnt like those much. then they started doing the thing where they introduce cameras into real world situations (for example the angry mechanic shows and the fishing shows), no prize but still a lot of sensationalism, setups, and overdramatization. there have been a few good ones, like mythbusters. but the problem with the genre is its everywhere. ive always considered reality shows (even the good ones) as filler for watching between the shows you actually wanted to see. and my major issue with reality shows is that everyone is doing them.
its like if every cable network up and decided to "lets do nothing but space operas", as much as a lot of people here would go for that. what do you think would happen? you would get 2 good scifi shows, and hundreds of bad scifi shows and nothing else to watch because every channel is clogged up with bad space operas. variety is your friend, and i shouldnt have to teir up my cable service to get some.