I should point out I've never played a burnt game... So that can't be the issue.
Not saying that the drive won't crap out if you don't play burned games. But like Cube said, the way the data is burned on the CD-R adds extra stress to the drive. It's one of those things like you're guaranteed to die at some point, but if you smoke, it'll probably happen sooner.
@MadeMang:
If it's only doing it when you're playing games/when it's accessing the drive, and it's happening with multiple games, it really sounds like it's the GD-Rom.
It would probably be cheaper, and less hassle just to get a new console, than it would be to buy and install a new GD-Rom Drive.