A weekend spent with MAME and this thread sounds like a fun weekend indeed. I think I might do just that.
For my input, the Gals Panic games that were on Super Nova hardware (S-series and 4). When people talk about the Super Nova system, you'll hear a lot about Cyvern and Sengeki Striker (good games, mind you, but they get way more attention than they're worth) and yet these gems rarely get a mention. A lot of people can't get past the "hentai porno game" stigma, but the gameplay is a well-refined Qix variant that sucks you right in. The frantic race to box the monster in off-image without sticking your neck out too far and getting killed is exhilarating.