Use the ioRTCW sourceport for widescreen and native resolution support. The campaign is a 9/10 experience, with some minor problems like enemies not flinching when you shoot them sometimes, and the final boss being underwhelming, but the combat is otherwise easy to get into and satisfying. Soundtrack is atmospheric and does its job, and you never feel like you're in the same looking place for too long thanks to a good mission variety. It's Wolfenstein at its finest.
The multiplayer was 10/10 and one of the finest of its era, too bad it's dead now.