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Space Channel 5 the first one was in English and probably Japanese as well, but I believe there is a Japanese version that is the sequel. My daughter really liked this game. Somewhere I have a complete list which includes the Japanese titles. What I recall, correct me if I am wrong, is Japan is NTSC so either will work Jap or Eng version of games.

Yes, both are NTSC, but I'm pretty sure that DC titles were region locked, so you needed a chip to play imports.  The burned games worked fine though, both US and Japanese, on either system.  

Part of the large number of releases was that Sega was still reasonably prolific at arcade releases, and the Naomi hardware was basically a dreamcast, so ports were really quick.  They also managed to release a ton of great fighting games from Capcom, and some really oddball games, like the Typing of the Dead (which is still fun on the PC).