I am returning to pc gaming and need some advice about games

I haven't play pc games in a long time. The last game I play was Half Life 1. I know that was a long time ago but I was occupied with console gaming, so I decided to come back and play some pc games. I really want to play some great classic games that I haven't played yet, games like doom 1 and ureal tournament 1. Can you please recommend my any classic games that are a must play. Oh yeah, I won't be playing any games before 1990. Thanks

I have listed some games I liked/like playing, and seperated them into categories. Games 5 or more years old are red. Games I recommend have a * after them.

FPS/Action-Adventure:

The Ultimate Doom*, Heretic 1*/2*, Hexen*,Unreal Tournament*, UT 2003, UT 2004*, UT 3 Duke Nukem 3D*, Bioshock*, Return to Castle Wolfenstien*(I REALLY liked the multiplayer), Quake Wars, Call of Duty 1*/2*, Call of Duty 4*, Battlefield series, Max Payne 1*/2*, Doom 3, Half Life 2*, No One Lives Forever 1*/2*,Ghost Recon, Ghost Recon 2, Rainbow Six series, Soldier of Fortune 1/2, Red Faction, Quake 1-3*, Quake 4, Team Fortress 2, Thief 1/2*, Thief: Deadly Shadows* Alien vs Predator 2*(good multiplayer), Star Wars: Dark Forces*, Freedom Fighters, Deus Ex 1*/2, Sanitarium*, Hitman 1/2,Hitman 3, Star Trek: A Final Utiny*

RPG:

Diablo 2*, The Baldur's Gate series*, Arcanum, Dungeon Siege*, Dungeon Siege 2, KOTOR*, KOTOR 2, Neverwinter Nights*, Neverwinter Nights 2*, The Witcher*, Mass Effect*, Fallout 1*/2*, Icewind Dale 1*/2*, Titan Quest, Morrowind*, Oblivion*, Planescape: Torrment*, Fredom Force, Nox

Strategy:

Starcraft*, Warcraft 2*, Warcraft 3*, Disciple 2*, Age of Empires 1/2*, Age of Empires 3*, Civilization 1-3*, Civilization 4*, Myth 2*, Black & White*, Black & White 2, Commandos 1-3, Warhammer 40k: Dawn of War*, Supreme Commander*, LOTR: BFME 1/2, Command & Conquer*, Command & Conquer: Generals*, Command & Conquer 3, Red Alert 1/2*, Company of Heroes* Empire Earth, Empire Earth 2*/3

MMO:

World of Warcraft, City of Heroes, Guild Wars (not a "true" MMO)

There's a lot more good games out there, but this list should keep you busy :)