The Dragon and Coco seem pretty under appreciated in most places it seems.
I've never used a Dragon myself, but my understanding is Dragon 32/64 and coco 1 and 2 are pretty much the same machines, but with different ROMs.
The coco3 was backwards compatible, but enhanced. Somewhat parallels a500/a1200.
Enhanced graphics modes (quite similar to Atari st there, but with only 6bit palette depth), faster Motorola 6809, updated ROMs, etc.
I was surprised at some of the game titles available when checking out Coco stuff online. Lots of big name games I was unaware of as a child.
Pitstop2, arkanoid, last ninja, gauntlet, legend of Zelda, thexder, zaxxon, Leisure Suit Larry and a bunch of others, both official and unofficial (don't know how they got away with some of the unofficial stuff though).
Gauntlet 2 looks pretty close to Atari st/master system versions, although its one of the unofficial games and is called "gantelet2". There's also a "gantelet1" for coco1,2 and Dragon which plays quite well, but of course isn't as nice to look at.