Dominions 4

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Recettear because I still play it a lot and it's a perfect example of how easily a game can pull you into its world, characters, gameplay, etc.

. Pac-Man
. Lord of the Rings : The Battle for Middle earth 2
. Commandos
. Rome Total war
. Warcraft 3: The Frozen Throne
& Age of empire/Age of mythology

GTA 3

As far as staying-power goes, my most-played games are Civ II and Zoo Tycoon (Complete Collection), but my "perfect" game is Tomb Raider (2013) I adore everything about it ♥

Too hard to answer that. PC Gamer did a top 100. Can´t even remember who is number 1.
My vote goes to Fallout 3 and The Elder Scrolls V: Skyrim
Hard contenders: Half Life 2, The Witcher 3.

I don´t know...It´s too complicated.

Has to be Doom. It's what like over 25 years old and people are still playing it today. And it still runs on modern machines. If that's not an achievement, I don't know what is.

Tetris(C)

Roller Coaster Tycoon (original)
The Sims (original)
SimCity 4

I must have put 1000 hours into each of these games.

StarCraft

Portal 2

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Super Mario Nurse Sisters

Witcher 3 is great but I really love Antichamber.

I have yet to play all video games on pc so I can't say :(

Tetris

Best PC game is on Steam. It's called The Graveyard.

Diablo 2 hands down

Taste.
This subjective aspect of the not too complex but far from simple human mind turns any vague measurements of 'quality' - in itself made of subjective paramaters - pretty much void.
Aka it will be different for everyone.

And heck not even that- im not sure wich of my favorites is above the other ones. If it 'is'.

This changes when theres more meat to the question. Like the best of a genre or the best at this or that featue.

The only way we can probably measure is by numbers:
Popularity, sold copies, ratings, reviews... even impact and inovation can in some way be 'measured'.

By those numbers the answer is clear:
The most praised, famous, sold, without a flaw, most original and most impactful with the biggest following not only in players but in 'copy-cats' and genre creating... Yeah, theres one like that (price and proportion of market being adjusted).

Its called

PONG

Not one flaw pointed out. The most original and impressive title that has ever existed.
Impressive both by its idea, execution, technical and technological inovation.
It had the most appealing gameplay with the broadest target audience imaginable. Decades before 'wii' non gamers who put their hands on it were amazed and having fun.
Even by design standards its an outstanding example hard to beat. No excess, doing its purposed without any fuss, incridebly intuitive controls not even a tutorial was needed. Its exemplary in minimalist design to this day but at the time it was the pinnacle as a whole- after all design is about getting the best results within the constrains. Unlike games that followed it didn't even tried to mimic images the thecnology couldn't portray at the time.
Nothing is perfect- there was no online multiplayer, no additional modes... but being skill based pvp it reaches that timeless endless replayability like chess or checkers- but considering its simplicity its obviously closer to tic tac toe. No learning curve. As deep as a rain pond.

But heck compared to todays gaming space it even holds some water.
NO BS DLC. NO FIRST DAY PATCHES. No lying marketing hype. NO BUGS FGS.
It ran flawlessly at top performance on every machine (their performance at the time).

It certainly had the most praise and units sold in comparison to market size of its time.
If games like HL, metroid and zelda are praised for their contibution to gaming thanks to their influences in some genres...
...this one probably influenced all of this.
It wasn't the first videogame and all of the earliest were big stepping stones- but from all the earliest wich is remembered, resonated? Btw pong was a door opener to videogame popularity- before it they were just... some curious thing computer guys did almost like curiosity, with low sales to niche computer guys. Arcades weren't even a thing until this motherfucker came along.

So there it is. By the numbers.
Pong.

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If i have to choose a single game it'd be X-Com 1994 . Though this discussion should be at least categorized by genres and then subdivided with other criteria

The Duke Nukem Forever we saw in trailers but never got

the rectangles you make while watching the desktop because you're bored and have nothing else to do ! ( ˃̣̣̥᷄⌓˂̣̣̥᷅ )

'Best game' is too contentious for me to give a good answer. Too many aspects for judging this, and this changes over time. A lot of the games I really enjoyed were because they made the best of the technical limitations of their time, and these days they'd look and sound like crap. A lot of enjoying some games was just me being younger. So just some stats and mentions

Longest game session I had was in Heroes of Might & Magic 3 (16-17 hours). The game I played the most was City of Heroes (I think over 1000 hours, but not totally sure). Game I played the most times: Peggle (but not necessarily the PC version; though I finished Peggle Deluxe twice on PC). Game I played the most times that's not casual: Neverwinter Nights original campaign (2.5 times). Game opening screen I stared the most at: Unreal castle flyby (though I didn't get far into the game). Game menu screen I listened to the most: Prince of Persia: Warrior Within (though never got past the tutorial). Only pure shooter I enjoyed and even played online quite a bit: UT2003.

I can't, I just can't pick one. I doubt such a thing actually exists, too many aspects to consider, too many almost perfect games but none without flaws of some kind.
If I really need to chose one that would be Portal 2, probably the closest thing I can think.

Populous: So early; so brilliant; mostly considered the first god-game

Lemmings: You may not fully agree, but I loved it so much that I beat all 150 levels. 2 of them took me hours to figure out.

Wolfenstein 3D: it had to be said. A great debt is owed by many to Blazkowicz.

Rise of the Triad: My first exciting multiplayer. Heat-seeking Missile was OP; still the Drunk Missiles were so cool. "Aaargh!" "Ludicrous Gibs"--getting hit by a military missile will blow your body into gibs all over the ground.