Worst game I ever played was Ancient Wars: Sparta. The absolutely must horribly glitched and buggy game I have EVER played in my ENTIRE life. A few bugs I have encountered:
1. If you have the demo installed, using the DVD-launcher to launch the game, will launch the demo instead of the full game.
2. Sometimes beating a level in the campaign won't let you go to the next level.
3. When you move the map around by clicking on the minimap, the screen will flash blank for a split-second.
4. Even if you don't play online, you can get messages saying you have been disconnected, and the game will exit.
5. If you change the graphical settings in the game and click the "restart" button to restart the game, it will crash and not restart.
6. Pressing "Home Page" in the DVD-launcher will take you to a russian version of the homepage.
A few other annoying things:
1. There is an unusual long pause in dialogue between characters.
2. If you mount soldiers on horses and load them on to a ship, when you unload them again, they will not be mounted on the horses, but stand beside them.
3. AI is ridiculously hard even on the easiest difficulty. It feels like when you are playing against a korean in StarCraft.
4. AI doesn't build ships.
5. You can't choose a resolution higher than 1600x1200 pixels.
The best game... hmm.. dunno. As much as I enjoy playing games with great visuals on my PC such as Crysis or Far Cry 2, I'd say it's Age of Empires 2. StarCraft is fun, but the AI is not noob-friendly