Over the years I have played video games but recently I've been more interested in finding good games to play. What I want to know is what games are worth buying and what games are not. 

The worst games I've ever played weren't professional and just fan-made stuff... but if you're talking about things that have actually been sold professionally... the Mega Man game for PC is maybe the worst I've ever seen. To be fair, it was made by a single person (despite being professional) so it probably should be judged equal to fan games. I've played many fan games of higher quality than this professional one... but those usually have multiple amateurs working together.

There's also a lot of really bad older games out there that I can't really think of off the top of my head... basically 70s and 80s arcade games were typically really horrendous with the rare exceptions being the well-known gems like Space Invaders or Pac-Man.

If you're looking for purchasing recommendations, though... I'm assuming you mean modern games? Should I instead have been listing the worst modern game I've played?

Hmm I believe that this belongs on another forum. I'm not saying that you did anything wrong, just that your topic might be more valid in another forum. Might I ask what system you want games for? Also maybe what kind of video game (racing, fighting, RPGs)?