In no particular order. Also, I'll cheat grouping games from a franchise together as one single entry... even so, I had to leave out many beloved games.

-Baldur's Gate (1 and 2 and expansions, including the infamous SOD)
-Icewind Dale (1 and 2)
-Planescape Torment
-Maniac Mansion
-Zak McKracken
-Monkey Island (1, 2 and 3)
-Thimbleweed Park
-Day of the Tentacle
-Legend of Kyrandia (1 and 2)
-Another World
-Drakkhen
-Civilization (1 and 2, haven't played the others)
-Syndicate
-Warlods Battlecry (1, 2 and 3)
-X-Com (UFO Defense and Terror from the Deep)
-Diablo II
-KOTOR (I've never been able to make the sequel work, so just the first one)
-Commandos (all)
-Desperados (haven't played the sequels)
-Shadowrun (SNES, Returns, Dragonfall and Hong Kong)

Baldurs Gate 2
StarCraft
StarCraft 2
Warcraft 3
Age of Wonders
Age of Wonders 3
Distant Worlds Universe
Master of Orion 2
Majesty
Alpha Centauri
FTL
DROIDWORKS
Rogue Squadron
Super Smash Bros
Civilization 4
Imperialism
Imperialism 2
MSG Federation vs Zeon
Ace Combat 3
Stronghold

1) Command & Conquer Generals
2) Age of Empires II
3) Rome: Total War
4) Europa Universalis IV
5) OpenTTD
6) Victoria II
7) Hearts of Iron III
8) Jedi Knight II Jedi Outcast
9) Skyrim
10) S.T.A.L.K.E.R.
11) F.E.A.R.
12) Battlefield Bad company II
13) Assassin’s creed
14) Europa Universalis III
15) Simcity 4
16) Far Cry 3

Thank you reminding me about Stronghold. I might go and play that this afternoon :)
Indeedy

I know its an old chestnut, but the thread has already served its purpose. Some great ideas of games I haven't tried, and reminders of games I really should play again

Thanks all :)

Ah, so I don't need to post my totally subjective opinion? Okey-dokey...

I'd love to see your list, if you get time :)
Subjective/objective opinions are most welcome :)

I don't do objectivity in art :)

Let's see:

01. Deus Ex
02. Heroes of Might and Magic 3
03. Timesplitters: Future Perfect
04. Devil May Cry 3
05. Soul Calibur 2
06. Metal Gear Solid 3
07. Silent Hill 3
08. Neverwinter Nights 2
09. Morrowind
10. Fallout New Vegas
11. Age of Empires 2
12. Vampire the Masquerade: Bloodlines
13. Dark Souls
14. Baldur's Gate 2 (Relative order from here)
15. Hitman 2: Silent Assassin
16. KotOR 2
17. Saints Row 4
18. Final Fantasy VIII
19. Freespace 2
20. Spec-Ops the Line

Thanks ;-)

TBS: Colonization
Adventure Game: Monkey Island 2
Racing Game: Carmageddon 2
RPG: Morrowind
Metroidvania: Hollow Knight
Roguelike: Rogue Legacy
Survival Horror FPS: System Shock 2
Rhythm Game: Audiosurf
Stealth Game: Thief III: Deadly Shadows (or how I play Deus Ex: Human Revolution)
3D Beat 'em up: Batman Arkham Asylum
Cinematic Platformer: Prince of Persia
Puzzle Game: Hexcells Plus
Puzzle Platformer: Trine
Puzzle FPS: Portal
Shmup: Skyforce Reloaded
Open World Action game (not sure what genre this comes under, we called in 'GTA-clone" in the old days :D): Saints Row: The Third
Endless Runner: Canabalt
QTE Adventure game (again, not sure what this genre is called): The Walking Dead Season 1
Top Down Dual-Stick Shooter (although I as always, play KBM): Crimsonland

I limited myself to PC games (except for a single SNES game that I listed as part of a franchise). If I had to consider my beloved Commodore 64 games and NES and SNES, it would have been impossible to reduce the list to 20. :)

Wizardry 8 (2001)- PC
Neverwinter Nights 2 (2006)- PC
Grand Theft Auto V (2013)- XBOX
Star Trek Voyager: Elite Force (2000) - PC
Might and Magic VII (1998) - PC
Fallout 4 (2015)- XBOX
Fallout 3 (2008)- XBOX
Fallout New Vegas (2010) - XBOX
Spider-Man (2018) - PS4
The Elder Scrolls IV: Oblivion (2006) - PC
Terminator 2: Judgment Day (1991) - Arcade
Rampage: World Tour (1997) - Arcade
Civilization IV (2004) - PC
DragonFable (2006) - PC
Aliens versus Predator (1999) - PC
Baldur's Gate - PC
System Shock (1994) - PC
Mortal Kombat (1992) - Arcade
Pac-Man (1980) - Arcade
Star Wars: TIE Fighter/X-Wing (1994) - PC
Metro Exodus (2019) - PS4

I will probably repeat many game others have mentioned, still:

Age of Empires 2
Alpha Protocol
Borderlands 2
Divinity 2
Divinity: Original Sin 2
Dragon Age: Origins
Fallout 3
Fallout New Vegas
Jade Empire
Kingdoms of Amalur: Reckoning
Mass Effect
Rome: Total War
Shadowrun: Dragonfall
Star Wars: Knights of the Old Republic
Stellaris
The Elder Scrolls IV: Oblivion
The Elder Scrolls V: Skyrim
The Witcher 1,3
Vampire: The Masquerade - Bloodlines

It should be 20, but I'm sure I've forgotten many more.

These types of threads are my favorites.

1. Star Control 2
2. The Settlers 3
3. Albion
4. OSP & Quake 3: DeFrag
5. Subspace/Continuum
6. Freespace 2
7. Factorio
8. Total Annihilation
9. Half Life 1
10. Gothic 2: Gold
11. Master of Orion 2
12. Stronghold Crusaders
13. Doom 1/2 (they're basically the same game anyway)
14. Baldies
15. Dark Souls 1
16. Mount and Blade: Viking Conquest
17. Darklands
18. Battlezone 1
19. Night in the Woods
20. Anno 1404

And yes, I've put Dark Souls 1 below freaking Baldies and you can't stop me 8)!

chrono trigger
final fantasy 6
final fantasy 7
secret of evermore
super mario bros 3
castlevania 3 dracula's curse
super metroid
the legend of zelda link's awakening
the legend of zelda (nes)
double dragon 3
mega man x
planescape torment
doom 2
elder scrolls 3 morrowind
elder scrolls 4 oblivion
ultima 5 warriors of destiny
might and magic 6 the mandate of heaven
duke nukem 1 (all 3 episodes)
divine divinity
quest for glory 1 (vga)