Traded my Atari and 50+ games back when I was a kid for some NES games. In hindsight it was stupid, but back then the games were worth $.25 a piece at flea markets and as a young kid I didn't know any better.
When it comes to consoles I still own, NES and later, I only buy games that I enjoy and will keep, so for older stuff emulation helps. I do still have some crap I haven't given away, and you can't help with new games. Just today I've bought and played the worst game I've played since the SNES. It's a fighting game, and I'd put this garbage alongside the magnificent quality of Rise of the Robots and Shaq Fu. I know I've only had it just a day, but the game is seriously that bad. There's no making this up.
The game I'm speaking of is J Stars Victory Vs +. The bad thing about this is that the DS game Jump Ultimate Stars was such a great game. I imported Jump Ultimate Stars and played it so much that I've hit 99:59:59, with over 3000 online wins and 1000 losses. Unless you collect everything, including games like the above listed Rise of the Robots or Shaq Fu, I'd recommend against ever purchasing this game for no matter what cost you see it for.
I'd say the other worst game I own is Wheel of Fortune for the NES. As a kid, I was at a video store, didn't have enough money for anything at the time except for this game and I didn't want to leave empty handed. It was less than the cost to rent a game because I didn't have the money to rent a game either.