The current XBLA offerings from Sega include, for the most part, games from the Sega Genesis era. Things like Sonic the Hedgehog 2, Ecco the Dolphin and Golden Axe. Thankfully, that's changing.
While the publisher is also bringing games like Virtual On Oratorio Tangram from arcades to home, it's also digging in a little deeper, apparently. The Entertainment Software Ratings Board has new ratings and descriptions for Shinobi and Altered Beast, which appear to be the System 16 arcade hardware versions.
Screens for those titles had leaked previously, as part of the rumoured "Sega Vintage Collection Vol. 2" series, but ESRB ratings are a very good indication that we'll be seeing them... and hopefully soon. Other titles rumoured to appear as XBLA releases include Genesis games Comix Zone, Sonic 3, GunStar Heroes, and Phantasy Star II.
If you can't wait for the arcade re-release of Shinobi, it's also available on Sega's excellent Sonic's Ultimate Genesis Collection for the PlayStation 3 and Xbox 360. Likely a better deal for die hard Sega fans.
Let's hope these wise decisions continue, ultimately resulting in more Dreamcast era and 16-bit arcade titles getting broader exposure. Any requests?