As for games with bad reviews? Never happened. I've bought plenty of games with bad review scores... but generally know what to expect and can pick out from a review if i'll like it or not.
HecK i bought the Beyblade game for PS2 for 5 bucks just cause i wanna see how they'd do it. I had enough fun in the cusomization aspects to cover the 5 bucks... which was really the only game part... trying to control a spinning top was really just giving it suggestions.
The only game i've been disapointed in that the jury is out on... is FF7. Which basically was the Godfather 3 of videogames for me. Not the WORST game out there.... but compaired to the legacy of the series it just falls short by a lot to the point of where it's painful to play.
I gave that game away, shame considering how much black label vesions of it went for on ebay later on. Either way i felt a few years later that it deserved a full playthrough... still was Godfather 3 but atleast i could say i played through it.