It has better gameplay than most games. Better Graphics. GPG is a multi-million pound company (im pretty sure).
It also has a pitiful 8 maps, no map making support, no mod making support, no replays, broken multiplayer, bad AI, a small community, no hype, no story, no cinematics worth a damn, etc. etc. etc. The release of a true AAA title is an event that whips the entire gaming community into a frenzy of excitement, and DG... did not do that. Unless you count all of the hate thrown towards the game at that time due to its worthless connectivity and the perception that SD was blaming pirates for it. That kind of frenzy doesn't count. 
I like DG, but I'm not going to pretend that its bigger then it really is.