Probably not the "best" games I've ever played, but definitely two most memorable:

I had plenty of great childhood memories playing TMNT2 with a best friend of mine (as well as the original Street Fighter) on NES. TMNT2 turned out to be a great multiplayer game as opposed to the first one , which had me pulling my hair out at times lol.
 
Aaaand of course HL2, but not simply due to its popularity (which I had no idea about). After the Sega Genesis played its life out, I went into a gaming hiatus from the beginning of 7th grade all the way until 2nd year college (games were just lost on me for that entire time, idk). Upon building my first PC, my dad of all people suggested I try out HL2, and well let's just say coming from Sonic the Hedgehog all the way to HL2 my mind was blown in ways I still can't fathom.       

All Mafias were great, all Stalkers were great, C&C's games
And undoubtebly the best games (wrong platform though) Last Of Us and Beyond: Two Souls

Half Life
Rise of Nations - I still play that game
Tradewars - the best strategy game of all time, still great but I don't have the time to invest in playing it anymore.

Some recent titles are definitely getting way too expensive, so I simply wait for the GOTY version to get on the discount rack
 

The problem with most of the best games I've ever played is that the nostalgia never quite matches up to the reality of them when I go back to them years later. I think what makes a good game is just as much that moment in time as the title itself.

Brad_Hawthorne
The problem with most of the best games I've ever played is that the nostalgia never quite matches up to the reality of them when I go back to them years later. I think what makes a good game is just as much that moment in time as the title itself.

DooM,  i still play it every day, and have played it every day since 1993. Yup, still holds up.

ARMYguy

Brad_Hawthorne
The problem with most of the best games I've ever played is that the nostalgia never quite matches up to the reality of them when I go back to them years later. I think what makes a good game is just as much that moment in time as the title itself.

DooM,  i still play it every day, and have played it every day since 1993. Yup, still holds up.

That's just it though, as you stated, you never put the game down for a decade and came back to it. You've been playing it rather consistently. On games people tend to remember from half a life time ago, more often than not a lot of that nostalgia is based off that time of your life and who you played those games with, not merely the game itself.

PS: Echo Night Series, it was my favorite game series. Way better than Silent Hill
PC: Sims and Project Zomboid
Mobile: Honeyday Blitz 2 and Fall Out Shelter. Those 2 games are my current favorite

Half Life 1 : My first FPS
Xwing vs Tiefighter : My first online muti player game. Spent a lot of time playing this online on Microsoft gaming zone.
Star Craft & Star craft brood wars. : My first and still favorit RTS
Tribes 1 & 2 : My ATF FPS. Still waiting on a real tribes 3
Asherons Call : My first MMO . Have yet to find another MMO like it.  When the game first started us Mages would spend hours at the local mage shop trying to learn new spells.  Good times
Free Space & Free Space 2 : My last space flight sim that I was really into
Fry Cry 1 : Mind blowing graphics for the time
Crysis 1 : I'm still kinda lost how the story from crisis 1 ties into 2 & 3. What happended to the blue aliens ?
Tron 2.0 : Yes a Tron game.  I always liked tron as a kid. Tron 2.0 has been the only Tron game that I have enjoyed. Heck you overclock an old computer from inside the computer ! How awesome is that .
Home World : The score, the visuals along with the first 3D RTS. Great Game
Portal 1 & 2
Stalker games
Bioshock 1: The ambience of this game was amazing . The story was also very good with some nice twist in it.
Fear 1: Blood dripping walls and a little girl that is freaky as hell
Jedi Knight 2 Jedi Outcast : I almost peed my pants when I met my first reborn. Finally after all these years I get to try out my lightsaber skills.
Vice City : 80's music !
Sim City 4 rush hour
Mass Effect 2. Loved the story .
Dragon Age 1 : spent close to 100 hours on this one. Hated DA2. Never played DA3 cause I hated DA2 some much.
Fallout 3. I work in DC so roaming capital wasteland was a lot of fun
KOTOR 1 & 2
Skyrim
Kerbal Space Progam : Landing a space craft on an outer rim planet was a major challenge . For those Kerbals that made the trip it was a one way ticket.  Sorry guys.
Just Cause 2
 
Its a long list but every game on my list was worth every penny .

Halo (all of them)
Alan Wake
BF4
Age Of Empires
Unreal 2003

I'm finally getting around to playing and finishing Stalker: Clear Sky. I've always loved the Stalker series and it's good to see that GSC Game World is back in action. I would love to see Stalker 2.

Kerbal Space Program
XCOM (original)