I'm really surprised a lot of game companies haven't been doing this more and more. Hollywood has been doing almost nothing but regurgitating old movies but just with slight changes (main character who was white is now black, or a woman, etc.).
With old PC games you don't need to make changes like that, just re-code the game with modern graphics (I'm sure there is a lot more to it than that, but you get the point). There are whole generations of PC gamers today who never had the pleasure of playing some really fantastic games from the 80s, 90s, even early 2000s.
I can imagine the early Ultima games, early Star Wars games (Dark Forces, X-Wing, Tie Fighter, etc.), Dune, Wing Commander, Star Trek: 25 Anniversary, Command & Conquer series, Indiana Jones series, Baldur's Gate and Neverwinter Nights series, Duke Nukem 3D, Dungeon Keeper, Lands of Lore, and a ton more (I really could go on and on, the 80s, 90s, and early 2000s produced some really great PC games) that would be amazing with modern graphics.
The old timer PC gamers would buy them out of nostalgia, and to all those who weren't alive or weren't PC gamers when those games came out they would be fresh new games.