[Retrospec] have made remakes of games from old computers, or original games inspired by old ones. Of the remakes, most notably, the games more-often-than-not first appeared on the Sinclair ZX Spectrum computer.

Check out their page, and try out some of their remakes. Some are better than others -- on the high-res end, I'd recommend at least [Head Over Heels], [Highway Pursuit], and [Jetpak: Solar Crisis] -- and on the normal-res end, maybe [Lunar Jetman], [Skool Daze: Klass of '99], and [Jet Set Willy] or [Manic Miner]. I'd at least recommend you try the high-res ones -- all of the games listed here have spiffy music, and the-high res ones, well, look incredibly spiffy. (The normal-res ones look spiffy too.)

Anyway -- it seems some of these games have ports to different computers. (At least Head Over Heels has a Windows, Mac, Linux, and BeOS port.) As such -- might there be any possibility of perhaps attempting Dreamcast ports of these games? There might be a memory issue (if the regular-computer memory requirements for some of the games are any indication) -- though I don't know if you might be able to develop any workarounds or such -- or, I don't know how much computer RAM requirements matter when considering console ports.

For anyone who might be interested in attempting a port -- though the sources for most games aren't readily available as direct downloads, perhaps you might be able to e-mail the authors about it. I'd imagine that might be how the ports to other computers for Head Over Heels were developed.