What I was best at and played the most was:

Heroes of Might and Magic 3
Grand Theft Auto (the first one)
Quake
Shogun: Total War (+MI)
America's Army
Enemy Engaged Comanche Vs Hokum
Alien Vs Predator (I&II)
Operation Flashpoint
Morrowind (+expansions)


All these games shared the factor that it didn't get old or boring. It always develops, whether it is in SP or MP. Obviously quake didnt change much in SP but in MP it was what I played most on LAN parties back in the day.