@sanity-check, you might be interested in looking into the various Decomp/Recomp projects going on which are basically doing just that. Somebody recently got Halo: Combat Evolved running in a browser window with 128 simultaneous player support and high-definition graphical upgrades.

There's a program called "Quiver" that serves as a frontend for a lot of these different projects, so you can download it and use it to keep up-to-date on over 200 games the community is working on. It's great stuff!