A lot of times I only start liking games in the last 2 stages (case in point, pid), so I can't really feel I can make a fair judgement in the game if I don't play till the bitter end.
So, I play bad games to completion so I can call it bad with authority. That's why Alan wake isn't good, and neither is okamiden.
I also like to enjoy the progression of a series, to see how each game improved or not something of the franchise. For example, final fantasy III is a horrible game, that failed spectacularly at the job system. At least on the Nintendo DS remake. Made me appreciate final fantasy IV even more.
But of course, nowdays even start good games is a struggle. So I don't consciously stop playing bad games, I just start other games and let it sit there by the sidelines forever.