Version 1.4.0 of Chocolate Doom was released recently; the project aims to replicate the behavior of the original DOS DOOM releases. I’m a bit of a DOOM purist, so this is the source port I use when I want to play single player. Moreover, developer Simon Howard was interviewed by Fragorama.se about the game:
Simon: There’s such a variety of reasons why people still play Doom. In terms of game play, I think some things are balanced in a unique way that is different to modern games – things like the speed of the player and the selection of weapons. I’ve seen comments to the effect that no other first person shooter is as fast-paced for deathmatch as Doom is. For single player, while modern games have moved on to one-on-one battles with intelligent AI opponents, the Doom gameplay remains enjoyable – slaughtering your way through hundreds of (comparatively dumb) monsters to reach the exit.
Also, my other favorite DOOM port, Odamex, is now at version 0.5.0. Multiplayer-focused, Odamex now has improved netplay and other optimizations/bugfixes. The team also requests that if you’re interested in assisting their efforts, please sign up at the Odamex bug tracker.