My top 3 is an easy one:

1. Baldur's Gate: Enhanced Edition

2. Dragon Age: Origins

3. Baldur's Gate II: Enhanced Edition

no. 4 and 5 is less obvious to me and will be coloured by the moment, I guess I'd go for:

4. Icewind Dale

5. Fallout 3

Battlefield 1942 used to be in my top 5 always, but by now it feels old. I'm hoping the trend to make all modern shooters take place in modern times will reverse and some good-looking shooters with single-player mode taking place in World War 2 will become fashionable again. Enemy Front wasn't my thing, I want to play on a true battlefield as part of an assault force, not a single resistance fighter with a mission.

Ummmm.................umm.....ah shit....sorry,got lost for..... a minute.........
1............................................................................................................. .........................................................................................................:)

That's what I was hoping for with C&C:Renegade years ago. At least the part where you fought on an active battlefield, sort of like the multiplayer portion of the game, only on a much larger scale. I still hope we get to see that game one day, even if it is a hybrid along the lines of Savage.

By the way, Verdun looks pretty good (WW1 though), but unfortunately it appears to be multiplayer only.

Morrowind
Dishonored
Minecraft
Dragon Age: Origins
Neverwinter Nights (modules)

Jagged Alliance 2 (Edit: added number)
FTL
Master of Orion (1 or 2)
Alpha Centauri
Space Rangers 2

Day of the Tentacle
System Shock 2
Binding of Isaac: Rebirth
Lemmings
Braid

Not exactly an accurate list of my top 5. I tried to come up with the first 5 games off the top of my head that I really, really like.

Yeah, there still are a few playing multiplayer but it migrated to steam when gamespy got shut down(Think you can register your old copies on steam though.). I feel the same about dow 2, I missed the carnage from 1 when I played 2. 1 is ridiculously fun.

I was a bug super smash Bros fan. Lots of good times in high school and college.

1: Thief 2
2: Skyrim
3: Deus Ex
4: Dark Souls
5: Half Life 2

1) Blade of Darkness.
2) Red Alert 2 Yuri's Revenge.
3) Diablo 2 and soon, this entry IS GOING TO change into Grim Dawn!
4) Vampire Bloodlines!
5) Streets of Rage Remake V5.1!

1) S.T.A.L.K.E.R Series (Can't pick one :P)
2) Doom (1 and 2. I consider them basically parts of a whole)
3) Half-life 1
4) Noctis IV
5) Myst

I would be lying if I say I didn't think a bit more. But that's because I don't really have top 5 favourite games, as there are much more, and I could not put one above the other.
But then again here are five of the games that came up first on my mind:

Old NFS Series
Mass Effect Series
Half Life Series
F.E.A.R. 2: Project Origin
Cognition: An Erica Reed Thriller

I like racing and story rich games. And the above are great examples of that

Tropico (1)
Fallout (1)
Primordia
Civilization IV
FTL

First 4 are pretty easy:

Baldurs Gate
Planescape: Torment
Baldurs Gate II
Dues Ex

Number 5 is hard. Maybe Thief? GTA3? NOLF? AoE2? Warcraft 2?

Easy

Bioshock Infinite
Bioshock Infinite Burial at Sea
Bioshock 2 Minerva's Den
Bioshock 2
Bioshock

Bam.