I'm 100% for quality. I mean, don't get me wrong, I have over 200 games, but they're ALL games that I would enjoy playing at any given time. Why waste time getting bad games that you know you won't play?
That being said, if I already own a bad game, I'm likely to not sell it. When I bought my Atari Jaguar, it came with 12 games, 10 of which I'm assuming suck balls, though I have yet to try them all. But, they came with the deal, so I'm likely to stick with them. Unless I ever need to make a quick buck, I don't see myself going out of my way to re-sell games I don't play. It just adds to the collection's diversity.