Before F.E.A.R., Undying was pretty much the benchmark of successful fusion of FPS and horror. Clive Barker helped shaped the game's plot and background that is somewhat inspired by Lovecraftian horror and together with Dreamworks Interactive's technical prowess at providing a tight and engaging gameplay experience, the final product is downright one of the best first person shooters ever made. One thing I liked about the gameplay is the usage of both conventional and magic weapons simultaneously, which I find lacking in modern shooters that implement both weapon types like the Bioshock series where you fire them separately. The Unreal Engine 1 looks terrible by today's standards though, and unfortunately due to the poor sales when it was released back then, there isn't actually a fanbase devoted to provide a HD mod or warrant a sequel. Something that you might consider if the graphics are a turn off.
If someone asked me what would be the top 3 games I've played with the best story, Anachronox would be one of it. Tom Hall has created one of the most underrated, underappreaciated RPG ever. Built on the framework of turn based JRPGs like Final Fantasy and Chrono series, Anachronox delivers a fresh take on the genre mixing cyberpunk, space adventure and even comic books with strong narrative and unique characters. If you're an fan of RPGs or just well written games you owe this yourself to get this.
Decided to buy this one when it was on sale, cause a decent resource based RTS is a rare find these days. Overall a decent effort with lengthy SP campaign, although one is left wondering why the other 2 races didn't get full blown one (only training missions are available). Budget and development constraints perhaps. The complaints I have is the pacing. Some of the units move very very slowly and the default game speed is actually slow. Might want to set it to highest.