halo 3 had something 170 million dollars worth of sales in the first 24 hours, they estimated that it was about 2.48 million copies sold in the first day.
the Halo series are some of the most epic games i've played.
wrath of the lich king sold 2.8 in the first 24 hours, it broke the record for most sales in 24 hours, taking it from burning crusade which sold 2.4 million, so halo must have been less than 2.48 in the first day.
I would probably say the most epic was the original c&c because of what it did for rts games. they were played and known of when c&c was released, but it really brought it right to the forefront of the popular genres and the cutscenes in it are iconic.
It was a toss up between that and warcraft 3 because although it was an rts game they gave such an amazing map maker that for the online games people brought rpg, tps, zombie and were the pioneers of the modern tower defence games. It is epic for its user made content which seemed almost endless, which is an amazing thing to do when the constraints of rts games seem so rigid
