Serious Sam first/second encounter.

Painkiller also. The first boss is just...well...EPIC

Outcast. Because all you get is epic.

The last level of the Second Encounter was maybe the most epic level I have ever played. Jaw-dropping!

You haven't lived until you've played the first boss in Painkiller, imho.

word

That moment in the first Unreal when you go from the ship you start off in to the outdoors...it may have lost a lot over the last twelve years, but that was a moment where you could feel awe at the world you were playing in.

The first Mass Effect game, several times, the first of which was probably less than an hour in.

Disgaea, when you start to realize how much there is to do beyond the main storyline.

Final Fantasy 7, if you can get past the translation and blocky graphics, as you being to understand the scope of the plot and the nature of the antagonist. Final Fantasy 10, also, for that matter.

Xenosaga, if you stayed awake through that one hour-long cutscene. You know which one I'm talking about.

Halo, if you were better at it than I was and didn't get stuck in a corner looking up while the enemies ate you, cursing at the gamepad for not being anything like keyboard+mouse.

Star Control 2, or Starflight 2. They're kind of the same game, actually, and both awesome.

Quest for Glory 1: So You Want To Be A Hero. The original EGA version, back when it was called Heroes Quest, with text parser. Or, if you were more of a Kingdom of Daventry fan, King's Quest.

Fallout, or Fallout 2, or Fallout: New Vegas. Not as much Fallout 3 or Fallout: Brotherhood of Steel. Planescape: Torment. Baldur's Gate 2 + Throne of Bhaal. Big games with a big world (sometimes worlds) to explore and change, and the feeling that what you do makes a big difference, even if you don't start out as king badass.

it hasn't lost anything. I played Unreal for the first time last year, and I still remember that moment. You step out and see this beautiful, baren landscape, and that music starts playing...

I love that game so much.

Betrayal at Krondor comes to mind.

Doom 2 level packs Hell Revealed 1 and 2. 69 monsters on the very first level, 114 on the second, then it takes off the training wheels. Level 22 got 82 Revenants [url=http://doom.wikia.com/wiki/MAP22:_Resistance_is_Futile_%28Hell_Revealed%29]http://doom.wikia.com/wiki/MAP22:_Resistance_is_Futile_%28Hell_Revealed%29[/url].

Final Fantasy VI.

You know a game is epic, when the world gets destroyed half way through it...

Star Control 2
By all the common rules of the universe, this game should be an unplayable mess, seeing as it's a space exploration / comedy adventure / resource gathering / arcade combat game with RPG elements. However, it all somehow comes together into one of the most epic games ever created. The story is fantastic, and the alien races are extremely varied and well designed, with excellent back stories. The mood spans from deadly serious to laugh-out-loud funny.

Giants: Citizen Kabuto
Kind of the same thing as above. It's a curious mixture of genres, incorporating gameplay elements such as shooting, squad control and base building, all garnished with the most outrageous humor I've seen in any game. It's not subtle at all, but it is ridiculously funny. If ever a computer game is going to make you physically throw up from laughing too hard, this is it.

No game surpasses the epicness of Commander Keen, try as they might. You might as well finish them.

Shadow of the Colossus

/drops the microphone and walks off stage

Okay...I am going to finish second one then :/

ahem you can't possibly just be saying that game on its own

ICO

and

Shadow of the Colossus

PS2 or HD remakes for PS3 represent oustanding games - utterly without equal! (heck just getting from place to place in shadow is a game in itself!). There is also an ISO 3 in the works for the PS3 (currently my only reason to really want a PS3!)


As for other great games, depends how you define great. I can list loads but most will be RTS greats .