I can't comment about HL2 or H2 simply because I've only ever played 2 FPSs in my entire life - Unreal Tournament and Doom... of those, I preferred UT... but I digress...

Seeing a peeps are mentioning their alltime great games, I thought I'd throw a few into the mix...

Azure Dreams on PSX - STILL playing it 8 years after initial (Japanese)release... Currently 110 hours into replaying it for the 7th time! Some people read LOTR as an annual thing... I play through Azure Dreams...
Also available on GBC, but I can't identify a thing from the graphics!

Grandia on PSX - The sounds are terrible, the voice acting is appauling and the graphics are excessively bright, but for some reason I LOVE this game... cannot say why... I just do...

Final Fantasy 7 on PSX- Just because... [troll] No matter what people say about 6, I replayed it recently after the last FF discussion (for a grand total of 64 hours this time), and I still don't believe the hype... don't get me wrong... its a good game... just not as good as 7... or 10 for that matter... but it's still better than 8... [/troll]

Also loving:
Star Ocean 3 - which I STILL have to finish!
Shadow Hearts: Covenant (with reservations about some of the hidden scenes...)
Breath of Fire 3
Ephemoral Fantasia (despite it being apparently universally reviled)

Sadly living in the UK we never did get our hands on Chronotrigger ot Xenogears...

Best game ever...

I'm gonna have to say the Worms series. From what I can think of, nothing compares to the timelessness and fun of Worms.

I mean, I love a game of Civilization III as much as the next man. It's epic, spans over the entire history of the world, gives you complete control and opens up so many differents strategies... but after the hundreth time you've built that spaceship or killed off the Babylonians, it gets a bit old. After you know what order of techs to do and what to do with all the cities, it just seems a bit tedious irrigating those tiles just like last game. To me, at least. mean, it doesn't stop me playing it still every now and then.

But even after playing Worms Armaggedon for years, that well-placed grenade is still as great to watch as the first time. That sheep landing just on that enemy worm, sending him into a mine... it's an absolute legend game.

I think I prefer the 2D worms games to the 3D ones. But that's just because I'm just a stickler for the classics.

[Nostalgia!]
Ooh...I'd almost forgotten about Worms Armageddon. I remember going over to a friend's house every day after school in grade 8 for...months, playing that game. Good times...
I should find that and reinstall it.

Scorched Earth, the Mother of All Games.

Classic, that.

Gotta love black and white thinking!

I've never understood the 'favs' thingy anyway. Its always good, great, meh or blech to me.

IMHO
Great RPG - KOTOR, Deus ex, Baulder's Gate series, Final Fantasy series, Vampire Bloodlines
Great FPS - Unreal Tournament 2000, Half life
Great Stealthy Sneaky games - Thief series, Deus Ex, Hitman 2
Great MMORPGS - EQ, CoH, EQ2
Just other good games I like - GTA, Pirates, Warcraft series (non mmorpg), diablo series, Chronotrigger

I agree with those who mentioned Alpha Centauri.

Also, Civ 4 is coming out. Soon I believe.

IS Sid Meier going to reincorporate some of the good things about Alpha Centauri into Civ4? If not... what's the point? :)

Will he incorporate the computer cheating? It always irritated me to lose half a dozen knights to a d*&n Zulu warrior thing.