The Sega SG-1000, Mark I and II.
What happened? This has to be Sega's least known, and especially least cared for system. I know it only saw limited release outside of Japan, but it really isn't that bad of a system. For 1983, it's graphics were quite good. The system had nice controllers, offered both card and cartridge formats, and had a good selection of titles, mostly produced by Sega.
It had some great games, Choplifter was a great port. Pitfall II (the arcade version), H.E.R.O, Elevator Action, Zaxxon, Zippy Race, were great too.
So, any other fans of the system out there? Any favorite games? I love all of the above mentioned titles.