Command and Conquer? Starcraft? Warcraft? Age of Empires? etc... which one made you stay late on the computer for days , weeks...just to crush the other army or to finish the awesome story.. For me it would have to be company of heroes and dawn of war - both games had amazing addicting multiplayer...I remember winning a dawn of war mp match after an epic rts fight and I was so happy I jumped up for joy!