So, some crazy dude or group just spent the time to convert most official Atomiswave games for the good ol Dreamcast. Contrary to common misinformation the hardware was near identical to Dreamcast (much more so than the beefier Naomi) outside the different format for the games (so depending on your own Dreamcast mod and method to run these can work better or worse though some fixes are available for others) and the input and other minor stuff, which was reflected in the dev kits. Granted, Atomiswave wasn’t a runaway success and several of its 20 something games weren’t anything to write home about as SNK also wasn’t at its best form back then but it would have cost SEGA and the other companies involved peanuts to port these and they would have made for a nice belated send off to the system and its fans as well had they published a few of the better SNK, Sammy and Arc System Works titles for limited release (and maybe a few of the not exactly great games like Ranger Mission if only to get more use out of the Dreamcast lightguns). Anyway, here are some of the better videos on this effort and the link is a page with links to all the original per game forum threads by the people who ported them, so far it’s the complete list. You’re right if you note that Guilty Gear X was officially released for Dreamcast in Japan, but Atomiswave got the newer revision 1.5 seen here. Of course it’s just the arcade games with freeplay, no extras/saves.