Zelda I, on NES.
Resident Evil 2
Grand Theft Auto Series
L4D & L4D 2
Payday & Payday 2
Kerbal Space Program
Star Wars Empire at War
Caesar IV
Age of Empires Series (Except Age of Empires Online)
Portal & Portal 2
Pikmin
Toy Soldiers Series
Warhammer Series (Including Warhammer Online)
Sniper Elite: Nazi Zombie Army
Killing Floor (Over 180 hours played)
Need for Speed Series
Borderlands & Borderlands 2
Dead Island
Arma Series
Command & Conquer Series (I have all the games)
Company of Heroes Series
All I can think of now. :/
Is there one game on that list you like more over the rest?
Cave Story
Diablo II (LoD, Median XL mod)
Minecraft
LoZ: A Link to the Past (+ Parallel Worlds hack)
Breath of Fire III
Wild ARMs 1
Nobody says World of Warcraft on a WoW emulation forum? I'm a little surprised.
WoW is my favorite game of all time. It has had a huge impact on my life and I've been playing it since I was 9 years old, I'm 17 now. Maybe its current state doesn't live up to what it once was, but that doesn't change my mind that It's still the best MMO on the market right now.