Here’s something to tide you over until Bungie releases its rebooted Marathon: there’s a freeware fan revival for the 1994 FPS known as Classic Marathon, and it’s coming to Steam “soon”.
This project is from the same team that brought us Aleph One, an open source engine built for current systems based on the Marathon 2 source code (meaning you can access Marathon, Marathon 2 and Marathon Infinity elsewhere, but not yet on Steam).
While the team has promised Classic Marathon on Steam will be an authentic experience, there are of course a few extra bells and whistles to bring this revival up to more modern standards. For example, there will be optional widescreen HUD support and 60+ fps interpolation, which will improve the smoothness of the animation over the original without breaking the game logic. This is “just in case the original is too authentic,” the Classic Marathon team said.