If you'd go with one GTA game to play in eternity, I'd think San Andreas would be the only choice, as it has the most mod support and has the most expansive, varied world of all the GTA games so far.

That would be UFO - Enemy Unknown or UFO - Terror from the Deep. I don't understand why they are not on gog.com yet. They are available on other platforms, cheap, DRM free - so gog -where is the problem?

But if you only have the original game without any expansion /mods /fan made levels? Doom and Quake are games that last just one weekend.

Warriors of Elysia is taking too long...

Yes, I'm well aware of how the (Ho)MM community accepted (or did not accept it) the 4th installment. I guess I'm one of the few that wanted more RPG elements in the strategy game, to be a bit more like original King's Bounty and MM series than HoMM series. It's a fantastic blend of both and I truly enjoyed BEING one of the heroes. I was actually completely let down by HoMM 5, although it did have a few nice perks of its own. #3 also did not sit well with me, I liked #2 much more.

I just hope there will be a MM10 or a HoMM6 sometime in the future and that would contain the spirit of old.

Thief 2. Great game with over 400 Fan Missions means several years of playability before you even start round again...

Deus Ex is another great game but there's not too much fan content for it out there. So my 2nd place would be Rome Total War - the number of mods is smaller than Thief 2, but they last ages. My current game of the Europa Barbarorum mod has taken 6 months and I'm half way through it :)

Edit - if we're going for vanilla games here, then I'd go with deelee74 and choose Fritz - you get endless replayability with chess, and Fritz is very good at scaling difficulty from a complete novice to an international grand master.

Might and Magic: Heroes 6 (the changed the name for some reason) is coming out sometime next year, and it supposedly has more RPG elements than 5.

Would have to be either Arcanum or Fallout 2...both have tremendous replay value, the customization of player-character is unparalleled. But then again, they were both created by the Troika team.

As soon as I know for certain I'm going to be on a deserted island, I'll pick which one. ;-)

The entire Quest for Glory series.

As far as a single game, probably a toss up between Morrowind and Deus Ex.

Thief 2 and a massive library of well made fan missions. Seriously, this is the greatest game ever made.

toss up between Baldurs Gate, Civ 3 and Total Annihilation.

Or sonic 2.

The Quest for Glory series. I'm waiting for it to appear on this site so I can buy it!

What about Oblivion with a whole bunch of mods?

Since I'm a competitive chess player (tournaments and online), I would have to agree with you. With me it'd be a chessbase product, Junior 10 (that's part of a family of chess engines, Fritz, Hiarcs, Shredder, Rybka). Thankfully, it has different modes of difficulty that emulate club and human-like play so you can fire up an opponent you have a reasonable chance of beating, as opposed to its full-strength engine, which you have *NO* chance of beating. The old expression that chess is an ocean where a fly can drink and an elephant can swim rings true, more than any video or computer game I've played. I don't know if online play is allowed in the "rules" of this thread, but if it is, all the better (chessbase products use their own server for human play). There really is no contest for me.

As much as I love my pet faves, eventually I'd get sick of playing Fallout or Baldur's Gate or Thief or Arcanum over and over. Sooner or later you'd memorize every tiny bit (and I do mean *every*) of dialog, and explore every nook and cranny, no matter how obscure, of the game and there'd be nothing but a husk left. Actually, I've reached close to this point with a good many of 'em already and had to take a break numbering in the years, plural. But in this scenario you're stuck with that one game for life, for good, as diversion.

But if I had to with something that is a "conventional" computer game...I'd go with Sid Meier's Alpha Centauri. Still the game with the most far-reaching depth that I've found, both strategically and with backstory, setting, and society cultures. The infinite varieties of the starting Planet with the varying factions boasts the most replayability, more than other world-sims or the Civilization series IMO.