Ulitimately, fun is more important than originality. For example: Portal is way more unique and creative than Half Life, but, honestly, I have more fun playing Half Life. As original (and fun in it's own right) as the gameplay in Portal is, the gameplay in Half Life is just more fun to me. This is probably a bad example though, because Portal is really fun as well.
So I'd rather play a game that is fun but unoriginal than one that is original but not very fun to play.
Quote: "i say u spend more time shooting combine (right?) and zombies than u do shooting aliens (i know zombies are counted to aliens, but i dont count em there.)"
As I understand it, the Combine are aliens.