Oh man, the 7800. Actually got one of those. Really regretted it since there were so few worthwhile games for it and so hard to actually find them!!
Before that, I had an Atari VCS, an Intellivision and then a 5200. Since I REALLY liked the 5200 (spent MANY hours playing
Space Dungeon and the port of the
Star Trek arcade game), I figured I should just go ahead and get a 7800, unlike my friends who were getting NES's and Sega Master Systems.
What sold me on it was in one of the early commercials for the console, they showed that they had a port of the Commodore 64 game
Karateka which I really liked, but hated the loading times. Figured I could get this game I really liked, without the dreaded loading time!
Only drawback was, the commercial showed footage of the C64 version, while the 7800 version was a watered down piece of crap. I learned then that (up until the present) console ports of PC games, much like arcade game ports, are quite far removed from the source material!!
Needless to say I got an NES shortly thereafter.
Another thing that probably kept Atari from going forward with the LD add-on, was the failure of the RDI Halcyon. Seeing how cost prohibitive it was and the fact that they could barely market the console itself let alone an add-on that would probably cost considerably more than the console itself (like seriously, I never understood how NEC thought the initial CD-ROM drive for their Turbo Grafx-16 made much sense since it was 2x the price of the console!!!), there was no reason to even try to go with it. Especially since LD games in the arcade had run their course by 85-86.