Plan9, near the end of the Genesis/Sega CD's lifetime there were no less than 3 different Genesis/Sega CD hybrids made by different companies. Different companies licensed the technology and made their own console, much like the 3DO was not made by the 3DO company, the company licensed the manufacture to Phillips and other companies who actually made and sold the console.
JVC Wondermega (Japan only)
Sega's own CDX which doubles as a walkman
There are more of these things but I can't remember the names of them, those are the most well known.
None of these were commerically successful or viable, I believe they came out around 1995 or 1996, they were still pretty expensive, and this was at the end of the Genesis' lifetime when better things like the Saturn and Playstation were out.
The Sega CD was a commercial and critical failure. Mega Man, sorry, but you're wrong. It did bad here, it did bad in Europe and it did horrible in Japan (because the Mega Drive did horrible in Japan- at this point in time the Japanese were into the PC Engine CD RPGs (Turbografx-16 CD here), as well as the popular Super Famicom stuff by Square). Truthfully, the Sega CD is an oddity, but considering you can get one cheap now and get free games for it I would definitely
say it's a good investment. There are a ton of great, unique Sega CD RPGs like the two Lunars, Dark Wizard, Popful Mail and Vay. If that's not your thing, there are a ton of fun and unique SHMUPs on the system like Lords of Thunder, Sol Feace, Keio Flying Squadron, Silpheed, Android Assault Bari Arm and Robo Aleste. There are high quality, close to arcade ports of Samurai Shodown and Fatal Fury Special, and an excellent port of Final Fight if you like fighters. There are the mainstay Sega games like Sonic CD (get the Jap version). Personally, I hate FMV games and none of the games in my CD stack are FMV games. Nonetheless, there are many unique, exclusive games that aren't on any other system, and playing them on the real hardware is a treat. Collecting for Sega CD is probably impossible considering how complete versions of nearly any Sega CD game go for $50-$500 on ebay, especially the expensive RPGs.
I love my Sega CD and it was worth getting. It was made before CD copy protection. Edited by neurotix - 6/11/13 at 1:58pm