Marathon offers some neat atmosphere, and was notable for being one of the first few shooters (alongside System Shock) to include mouselook aiming.

Aside from that, there's nothing about Marathon that has aged particularly well, nor is it particularly worth visiting in modern times outside of a curious look into the roots of Halo and Bungie's history with first person shooters.

Nothing about the enemies or weapons is exciting, the level design is unengaging, and the controls have somehow aged awkwardly.

Unfortunately, Marathon is just another one of those weird niche shooters that doesn't have the modern luxury of an excellent source port.