I bought Steel Battalion a couple of weeks ago. £116. Hefty whack of money and a hefty game. 'Cept now it's a hefty sitting room ornament. I've hardly played it and, honestly, don't think I'll get much use out of it. It wasn't a good value purchase.
Battlefield 1942. I bought that in 2002. It cost me about £30. I also bought Road to Rome. That cost about £20. I played BF1942 regularly for about a year and half. I was part of a long running tournament, got the Forgotten Hope mods and really squeezed that game for value. In terms of cost/benefit, that's probably been the best game I've ever bought.
What's yours?
I''ve not played it in awhile, but Diablo 2 went a long way for the buck.
In order:
1) Subspace: One of the few that actually owned a boxed copy of the game, the number of hours I put into it are incalculable.
2) Warcraft 2 : At the time I had a Mac and this was the only decent game I had for it. Thus it was the only game I played. For a brief shining moment, I was a God.
3) Half-Life: Tack on CS and my infatuation with Half-Life''s deathmatch and I may have lost a year of my life to this game.
Like Dr_Awkward, I''d also list Diablo 2. That Battle Chest has to be one of the coolest and most awesome games I''ve bought.
Something more recent (and multiplayer, as opposed to Diablo''s singleplayer) would be Unreal Tournament 2004. Been playing that basically every night since I bought it (which was somewhere around the end of March), so that''s working out great for me. 
Good call Elysium. Subspace was indeed the cat''s ass.
Starcraft & System Shock 2 co-op multi
another Halflife victim here. Couldn''t stop playing Day of Defeat. Followed by the quickly catching up Battlefield 1942.
Edit: Yeah halflife was the best value, found it in a $5 bin.
Mario Kart (SNES version) thanks to hundreds of hours spent on time trial and match races against friends. Civilization 2 and Sim City 2000 for sure are among them. So is the Gameboy installment of Tetris. International Super Star Soccer 64, of course. Jimmy Connors'' Pro Tennis Tour on SNES happened to be our tennis game of choice until Virtua Tennis arrived.
hmmm
Halo
Still having LAN parties to this day...
After that.....ESPN FB
Quake 1 - I played it for years. Technically I never bought it. I played Qtest, the shareware and the full version came with my video card or sound card.
Others of note are MW2, Diablo2, MC2, Might and Magic 3, and Diablo 1
HL, Diablo 2, BF1942 and Civ 1/2/3.
Ummmmm...
MechCommander 2... It''s STILL on my hard drive... and I doubt it will ever leave.
Rise of Nations probably, just by doing quick battles, I''ve put more hours into it than the typical FPS. And yet, somehow, I still suck in multiplayer...
UT2004 for sure. I''ve been playing it almost every day since the day it came out. I''m not entirely satisfied with the mod scene yet, but I''ve loved all the community maps and models and such.
Diablo II took up way too much time and the phone line for far too long when I was still on dial-up.
Morrowind comes to mind. I didn''t figure it out at first, so it sat around for a while, but once I got into it, I''ve put more hours into it than I really care to admit. Add in all the beautification mods, and well... yay ^_^
GTA: Vice City has definitely put in some LOOOOOOONG hours too, hehe. Just driving around shooting stuff and trying to find all the sercret jumps and packages has sucked up a lot more time than it really should have. I''m scared of what I''ll do with San Andreas.
I''d say Neverwinter Nights was a big one too. I played it online with a group ""A Land Far Away"" which was a whole set of persistant servers set in the Forgotten Realms. Helping out with building and then going back to playing and role playing and helping out newbs in the community was awesome, especially with the real D&D rules, even if I never could get past level 3.
The last PC game that comes to mind is Deus Ex... I missed punching in the keycodes myself... always was fun.
Console games I''ll just list... Suikoden, Suikoden II, Street Fighter Alpha 3, Tales of Destiny, Crash Team Racing, Front Mission 3, Sonic the Hedgehog 3...
I think that''s it... wow, I spend way too much time with games.
PC: Deus Ex, Half-Life, Fallout Tactics, Planescape Torment.
Mac: Diablo 2, NeverWinter Nights.
Xbox: Halo, Ninja Gaiden.
PS2/1: Final Fantasy VIII and IX.
[edit]...NFS3 for PC.
As much as I hate to say a game that I paid a monthly charge for is value oriented, I would have to say EQ was by far the most timewise I have ever played a game and must be on the list. As for normal games I would go with Pool of Radiance and Zak McKracken and the Alien Mind Benders as the two I played the most of, but really that was only because I was a kid and couldn''t buy any more games than the one''s I had.
Baldurs Gate 2, Planescape, and Fallout 1 & 2 were pretty good bang for the buck but only because they took a while to beat, not because I played them over and over.
Definitely Neverwinter Nights - still play weekly with friends.
Although I''ve not used any of the mods - the gameplay you get from Baldur''s Gate (all versions and expansions) has to be the most (or very close to the top of the list) bang-for-the-buck ever in a game series.
Civ 2. Gotta be in total hours played around six months. Never thought about that before. Very disturbing.
Half-life easy. When you include death match, CS and DOD, the gaming went on forever.
Soul Blade/Calibur/2. The various incarnations of this, the best fighting game ever made, have given me insane amounts of value and playtime. This is the most fun you can have with a group of guys in the same room without devolving into homomexuality.
Baldurs Gate II I played this for 11 months. The game is frickin'' HUGE if you do most of the quests.
Diablo II What is there to say that hasn''t been said?
Battlefield 1942 Great value, great game. BFV has a shot at making this list over time too but needs some good mods ( a la Desert Combat) and more maps
Unreal Tournament I put a lot of time into this game. I even learned UnrealEd and designed several maps. The mods and continual free content from Epic Help throw this one to the top of the heap.
Honourable Mentions Although I haven''t played them to the full extent of great Value myself, Half-Life, UT 2004 and Morrowind are packed with great content and have the potential of providing countless hours of gaming goodness.
Hmm... it took me an hour to finish this at work here and there were 7 replies when I started. I bet I see a lot more after I press submit.
All time has to be Quake 3 Arena. I can''t say I bought my first PC for it (I was a Mac gamer originally) as I really bought it to play UT, but once I got it, it has been on my systems ever since. Still jump in with my clanmates on occasion.
For my Xbox, PGR2. When I sold it I had put in over 90 hours in single-player. That''s obscene to me.
As far as an overall cost/time spent ratio, the two leaders in relatively recent years would be Diablo and Battlefield: 1942. Looking backwards it would be likly be Mule on the C64.
In absolutely no discernable order:
Jagged Alliance 2
Diablo II
Starcraft
Halo
Jedi Knight
Starcraft, Counter Strike, and halo.
Unreal Tournament and Bard''s Tale are the two that come most readily to mind.
HoMM III - Hundreds upon hundreds of hours.
Doom II - I''ve replayed it more than any other game.
Unreal 2004
Diablo 2
Half Life
CIV3, Alpha Centauri, BG2, Diablo 2, Half-Life and BF1942 and all its mods by far. No particular order, but those are probably the ones I have had the biggest bang for the buck.
Jagged Alliance2, Heroes of Might&Magic 3, Civ3 for my wife. Strange.. its not that I`m hardcore strategy fan.
umm..Disciples2 as well. God only knows how many hours have I spent playing and replaying various heroes for various races.
Pirates for my C64 I''d guess. PLayed that game hundreds of hours!
Oops - I should have mentioned Half Life too (no pun intended), if only because I played CS all the time.
SNES Super Mario Kart: fantastic game. I had a friend at university who played that instead of going to an exam. (He knew he''d fail, but he also knew he''d get a re-sit.)
Baldurs Gate 2 (favourite game series), Morrowind and Operation Flashpoint for Coop.
Between the 3 we''re looking at 1000 man hours of useless but highly entertaining time spent.
BG2 and its brothers simply because it''s the best RPG ever made... don''t argue. 
Morrowind because its the second best RPG ever made... also don''t argue. Its mods make the game endless, thats what I call community spirit.
Operation Flashpoint because I think its the ultimate coop game, extremely easy and powerful map editor and hundreds of new units to try out and play.
I can still see myself playing these games in 10 years time.
Cost of each game with expansions £60. Money well spent.
In my case, Starcraft has the best price/longevity ratio by far.
Pages