In no particular order:

• Megaman X
• UNDERTALE
• Call of Duty 4 (campaign, never played MP)

I just really like those three games. They're all fun in their own ways and in the case of Undertale it shaped a huge part of my 20's because it was through playing it that I learned to love humanity even with its bumps and scrapes. It kept me from turning into a full on misanthrope.

Honorable mentions go to GTA Online (I have almost 6000 hours in that game total, it's my favorite pastime), Call of Duty Black Ops 2 (multiplayer), and Titanfall 2.

1. Mafia 1 from 2002, that game really shaped my taste in games when I was a kid
2. Kingdom Come Deliverance 2. Essentially a perfect video game from start to finish IMO.
3. Alan Wake 1 or 2, genuinely hard to pick one.

Master of Orion 2
Lords of the Realm 2
Caesar 3

Metal Gear Solid 3, Subnautica, Papers Please.

I love the Metal Gear series but the Cold War setting of 3 works so well with the theme of the game. It also features crab battles and the ladder boss.

Subnautica really captures the feeling of being lost in some alien world and slowly making it your new home. The electronic voice assistant manages to send chills up your spine with lines like "oxygen."

Papers, Please explores complex moral decisions in such a simple way. I wish to live my life more like Jorji.

1. Super Metroid
2. Fallout: New Vegas
3. Factorio

Assassin's Creed: Black Flag and Rogue. Skyrim. Dishonored. Bioshock. NFS MW (2012). The Pentiment. These are in no particular order.

• Gothic 2, and by extension, Chronicles of Myrtana
• The Binding of Isaac: Rebirth
• Both are equally as monumental, so it’s shared between Obra Dinn, and Outer Wilds

That being said, i’ve excluded any mmos out of this list, purely because sometimes i struggle to call them my favorite games, despite having playing several thousand hours of each. Some of them have been unbelievably impactful at certain times in my life, but i’m afraid the embers are getting cold now

Favourite of all time?

Wing Commander (2 if I have to pick one, otherwise 1, 2, and secret missions).

Monkey Island (3 if I have to pick one, 1 to 3 otherwise).

Third is difficult, but... Disco Elysium, I guess..?

(What games I've spent the most time playing, though..? Definitely Crusader Kings 2 and 3, followed by Stellaris.)

Off the top of my head, in no particular order:

• Portal (or maybe Portal 2)
• Doom (the 1993 one) (or maybe Doom 2)
• Stellaris

All great games

For me it’s always about how much fun I had playing them, so right now and in no order:

• Halo 2
• Starcraft
• Red Dead Redemption

Honorable Mentions:

• Super Mario World
• Super Metroid
• Ocarina of Time
• Fallout: NV
• Assassins Creed: Black Flag
• Deep Rock Galactic
• Hades
• Hollow Knight

Duskers, Homeworld & Earth-2150

Now this is a tough one to be honest. But if i had to pick:

1. Cyberpunk 2077
2. Sekiro: Shadows Die Twice
3. Hades

Honorable mentions (cant leave these out): Return of the Obra Dinn, Wasteland 2, Darkest Dungeon, and many more...

Call me Nostradamus 'cause it's Silksong.

1. MGS3
2. Metal Gear 4: Peace Walker
3. MGSV

Honourable mentions: Metal gear, Metal Gear 2, Metal Gear Solid, MGSV: Ground Zeroes and Sons of Liberty

Today:

• Super mario world
• Shadowrun Dragonfall
• Mechwarrior 4 mercenaries

Outer Wilds

Mario Galaxy 2

UFO Enemy Unknown

Half-Life 2, Max Payne 2 and Mass Effect because I‘ve been an impressionable teenager and a nitpicking adult.

• Quake
• Minecraft
• Fallout

It's hard as there's a lot of different games that I like for different reasons, but if I had to narrow it down it'd probably be:

• Minecraft
• Mirror's Edge
• Dragon's Dogma

• Oldschool RuneScape
• Factorio
• Baldur's gate 3

No one is going to agree with me, but here I go:

• Counter Strike (all versions): the perfect shooter.
• Terraria: the progression is amazing, but what never ceases to amaze me is how, despite the game's huge content, it is never overwhelming or intimidating. Just a lot of fun.
• Transport Fever 2: by far my favorite world-builder type game, and it still gets updates!

1. Portal
2. Disco Elysium
3. Drone Perspective

In no particular order ( mostly cos i think ranking beyond a certain degree of precision hurts the art involved ):

• NieR Automata
• NieR Replicant (ver 1.22.. , realistically)
• The Talos Principle ( one of the most suprisingly brilliant games that too many people haven't played)

then i suppose one tier below, not consequent of any particular shortcomings, but rather just not being at the same "transendent" level as the above:

• Crosscode
• Citizen sleeper
• What Remains Of Edith Finch
• Portal & 2

NieR automata literally changed my life, so it kinda deserves it's own top spot, but placed as is in spirit of the question.

1. Horizon: Zero Dawn
2. Ghost of Tsushima
3. Legend of Zelda: Breath of the Wild

• Mindustry, it's open source as well, must have sunk close on a thousand hours into it. Incredible Game, has a good modding scene as well.
• Trove, the opposite of Mindustry, in that the game sucks, I do not recommend. However the game had so much potential and it sort of half realized it before becoming a cash grab. Does a good job of releasing LOADS of dopamine for very simple game play. That said I am now looking into Veloren - which appears to try and be a better version of trove, although taking voxel MMORPG in a new direction. It's also open source so, yeah.
• Minecraft - with mods. Nothing quite beats tech mod mania. I hope some day luanti gets to be a real competitor on some level, but till then.

In no particular order, and without adjusting for recency bias:

Single player

• Hollow Knight
• Undertale
• Outer Wilds

Multiplayer

• The Finals
• Awesomenauts*
• YOMI Hustle

* Right now the game is in a weird state where the original company who owned it went backrupt, and the game is in the process of being revived by a different company. In the meantime, the already low player count got lower. On top of that, there's two versions of the game: an old version that used Steam matchmaking (as the matchmaking server went down when the game original closed); and what had been the current patch, being accessible on a beta branch, which currently has issues making it hard to actaully play a match.

1. Oldschool Runescape
2. Halo 2
3. GoldenEye 007

• Uncharted (series)
• RDR2
• Minecraft

Honorable mention: No Man’s Sky

Civilization (the OG dos version)

Planetside 2

Warframe

• NieR: Automata (Replicant is also as good)
• Metal Gear Solid 2
• Yakuza 0