I changed the topic title for you, no worries.
When people think of retro console games, they tend to think of NES, Genesis, and Super NES. Those always seem to come up as the top three. You see things like retro consoles made to play cartridges from those three platforms, for example.
Yet here on VGMaps, the NES and Super NES have consistently had the most popular pages, and while the amount of Genesis maps we have is nothing to scoff at, it's never quite as close to the Nintendo consoles' amount of maps as I imagine it could be. There seem to be a lot of Nintendo fans here (not that I've mapped much at all, but I am one of them too), but Sega should get more love. Perhaps there are technical issues too (whatever features are available in emulators, etc.). Though I guess it's easy for me to simply talk about it...
Will, since you already seem inclined to do it, maybe you could make your "Genesis Game Atlas" topic anyway, without necessarily waiting for the Master System/Game Gear one to finish. It would help draw attention to the Genesis atlas a bit more, and especially to fulfill the series it's known for.
(Oooh...I'd like to see the Sonic The Hedgehog "trilogy", along with Sonic & Knuckles and how the "Lock-On" alters past games' maps.)
Back to this topic...you could also try messaging the mappers that started mapping these games, to see if they can, or wish, to complete them.