My favs are
AND HACK AND SLASH
AND HACK AND SLASH
I loved CnC and Red Alert. I also played Starcraft and it's expansion, Brood War. Never played the rest though. I also have to agree with the shooters. I've played all of them except for Unreal and Quake III.You guys know how to bring back memories...
Let's get this party started!
Diablo 2 LoD
Sacred Underworld - this was the first game I played that had a huge open world to explore with lots of side quests and Easter eggs to discover.
Lionhearth: Legacy of the Crushader - it used Fallout's S.P.E.C.I.A.L system. Exiled Kingdoms use a similar system ( awareness = perception and personality = charisma, but luck is missing)
Dungeon & Dragons
Neverwinter Nights: Hordes of the Underdark
Path of Exile
The Elder Scrolls: Skyrim, Oblivion and Morrowind - even today, after 8 years, these games can surprise me. The lore Bethesda built over time it's like an endless stream of good books to read.
The Witcher 3 - i'm planning to get the first and second games as well.
Command & Conquer '95 - I remember you could take down a Panzer with a just a Grenadier, but one small mistake and you man ended up crushed like a bug. Unfortunately they removed the ability to run over infantry in later games...
Red Alert 2 - I used to play this game with my colleagues over LAN. Lots of good memories...
Starcraft: Brood War
Warcraft 2: Beyond The Dark Portal
Warcraft 3: Frozen Throne - the birth of a new genre: MOBA
Heroes of Might and Magic 3 and 3.5 (In the Wake of Gods mod)
Quake 3 Arena
Counter Strike 1.5 and 1.6
Return to Castle Wolfenstein
The Legacy of Kain: Soul Reaver 1 and 2, Blood Omen 2 and 1 and Defiance - this is the order I played them. I liked Soul Reaver 2 the most. The story and the ending is just epic.
Devil May Cry 3
Skyforge - before they ruined it with Ascension patch.