Maybe he'd like to try something more.... recent, mate?
If you're just entering the gaming arena, Don, I'd recommend trying something out from ValvE through Steam. Their online catalog is quite extensive, and you can find some pretty main stream stuf there as well as serious FPS's (as well as strategy games, adventures, etc) and I'm sure you'll love their online delivery system. All it takes, is a credit card, and a reasonable internet bandwidth. You can download the game and play instantly.
Bioshock is available through Steam as well, but you may want to read some of the threads here about the DRM policy involved. Prey (also in the Steam catalog) might give you a nice bridging between the original doom experience and how shooters have since moved then.
There are other online publishers out there as well, just do some googling. I don't work for ValvE or have shares, I'm just a satisfied Steam customer.
Edit: I have to be fair to Bomber, as already stated in another topic, FarCry is now available for free (it has some ingame advertising in it now), and if your last experience was the original Doom then I think FarCry will give you a very satisfying experience for an unbeatable price, even if its now an outdated game (released in 2004).
Enemy Territory: Quake Wars next month, or you could try out Battlefield 2. It's over 2 years old, but not bad looking, still alot playing it.
Half Life 2 is great, and episode 2 is coming out next month. (in the process of finishing episode 1 right now.)
Bioshock was simply the best singleplayer experience i've had since farcry, and half life 2, but farcry and hl2 singleplayer has a bit more replay value imho, maybe it's because I just finished it, i'll see how I feel when I get my new rig in the next week or so.
Because there have been multiple mentions for the original Half life game, I would like to add the possibility of playing Half-Life: Source. It is the same game (Half Life 1) but using the Source engine instead of the old one. Quite an improvement in terms of physics although the textures are seriously outdated (of course). There is a project ongoing to update all the textures as well but I haven't heard about it for a while. Anyone else know about that?
I'm really busy right now with work but when I get the chance I continue my room to room journey through Doom 3.
I can understand why certain gamers didn't like it, but I think it's a great game. It's incredibly intense; probably the most intense prolonged gaming I've ever experienced (FEAR was more creepy but IMO doesn't match DOOM 3 in that regard).
When I played HL 2 I loved it but I never felt challenged by that game. In DOOM 3, on the other hand, I feel like I've used all of my gaming skills to survive (I'm not a great FPS player). I've definitely had to improve my skills just to maintain enough health and armor to move on.
It's rapidly moving up my list of favorite games. I guess I've never had trouble suspending disbelief for these types of experiences.
As a reviewer said: It's the only game I've ever played where I'm actually happy to die sometimes just to get some relief.
Surprised no one said Call of Duty 1 and 2 yet. Get FEAR if you haven't, maybe Stalker (I liked it at the time, but going back I really notice how incomplete it is). Play bioshock demo to see if it's your thing, it definitely was mine.
FEAR, Call of Duty 2, Lost Planet (PC Version), Half Life 2, Doom 3, Quake 4, Stalker: Shadow of Chernobyl (RPG-Shooter Hybrid), Bioshock (RPG-Shooter Hybrid), Prey, Far Cry, and Rainbow Six Vegas.
If you like extreme tactical shooters like myself, Ghost Recon Advanced Warfighter 1 and 2, however don't play the crap dumbed down Xbox versions (On both Image quality and gameplay), because they are a complete different experience than the PC is (Especially GRAW2).
Upcoming important shooters: Crysis, Call of Duty 4, Unreal Tournament 3, and maybe Gears of War (Complete version i.e. PC version).
Note: Nobody really uses joysticks anymore, and the absolute best interface to play shooters on is a Keyboard and a mouse anyway.