Hmm would have to say Turbo Duo. Not only does it play games very nicely still after 12 years, the build quality is amazing! Very solid plastic, rugged CD-ROM mechanism, reads burned CDs, and has a homebrew following/demo scene. Also if you happen to have the pleasure of owning one, hook it up to your stereo. You will be amazed at the clarity and crispness of the CD audio playback.
Runners up:
Sega Dreamcast (Moderate success)
Sega Saturn (Doomed because of the SegaCD and 32x fiasco)
