They're better off as full retail releases though. Cave probably wouldn't have gone the extra mile redrawing the spirtes for HD, adding in new modes, developing DLC, etc. for a $10-$15 XBLA release. Like when (if?) Guwange comes out, I'm sure it'll be exactly the same as the game you can play on MAME along with achievements and leaderboards.
Anyway, I'll be getting at least one copy. I might buy 3 more for Christmas presents, but I'm kinda broke.