Let's see here...
1. Castlevania: Symphony of the Night - Yeah Konami wants to reboot this series, but putting this on Steam (or on GOG/Humble Bundle to get it DRM free) SHOULD earn them more money than what their reboot is (probably) earning them. Hell, charge $10 bucks for the game, another $10 for the soundtrack and it would be worth it.
2. Shadowrun (SNES) - I really like "Shadowrun Returns" on Steam. It's great to come back to the dark alleys of Seattle so I can hurl Fireballs at cybernetically augmented gangsters. But THIS Shadowrun game was my first introduction to being a runner, and I would love to play this again. It almost feels like it would work well with a mouse too, considering a lot of its interface relies on mouse-precision.
3. Shadowrun (Sega Genesis) - I got into this beyond the lifespan of the Sega Genesis, but heard some good stuff about this game. I had a lot of fun with the Matrix portion of this game, and I still think it is the best interpretation of the "Matrix" of the three Shadowrun games.
NOTE: Make a bundle of both Shadowrun games for the PC and you'd have my money quicker than the Millenium Falcon jumping to light speed.
4. Any "Mana" game - Specifically: "Secret of Mana", "Seiken Densetsu 3", and "Legend of Mana". "Secret of Mana" was a game I played to death in my youth and I could see myself getting back into. "Seiken Densetsu 3" is something I only played a bit and read about, but the idea of picking your party members and having to alter your linear-JRPG route to collect those characters intrigues me. But the real prize for me here would be "Legend of Mana". Custom world? Multiple side quests with epic boss fights? Fantastic soundtrack? Excellent replay-value? That game NEEDS to be on the PC.
5. Secret of Evermore - Over the years, I kind of respect this one more over "Secret of Mana". They are both great games, but I kind of like the setting and story this one more. I'll agree that the depth of weapons and especially the broken spell system doesn't make this game better than "Secret of Mana". However, in this game you get a mecha-dog with a toaster body that fires lasers from its eyes. LASERS! And you get a Bazooka.
6. Demon's Crest - It's a pretty awesome platformer game from the SNES era, probably considered a "metroidvania" game by today's definition. It doesn't have one huge world, but there is a lot of backtracking through previous levels to find new items that couldn't be acquired before hand. Plus you get to play as a Demon that can fly as long as you want in the air. Personally I would love to see Capcom do another sequel to this series, but just playing this game again would be great.
7. Mega Man X Collection - I still think X4 is the best one in this series, but the first three games on the SNES were really good. I fell out of the series after X5, probably because they nerfed Zero (in my view). But I still would like to have this series show up on the PC. It would also be nice to get X4 without having to pay a $100 for the actual PC version. >.<