yeah half-life won game of the year, its the only game i can think of that ever won it
it was described as the closest thing to an action movie, and I certainly is. Thing about Halo is that its just constant shooting, then some really good vehicle scens (the banshee rocks, wish you got it on multiplayer) but Half-Life has more interaction with your enviroment.
I'd like a Sequel, maybe you are Gordan again and your fighting with the goverment against the Aliens again.. who knows?