Syndicate is one of my all time favorites. I could never get into the Syndicate Wars demo, so I never played the game. A straight remake of the original Syndicate would qualify as innovation compared to the console games we have on the PC right now.
God, there's nothing quite like walking your 4 little trenchcoats with bright orange hair nonchalantly down the street, hands in pockets, then BAM! each one whips out a minigun and lets loose on the target. I remember getting back to the dorms after my 8:30 class and firing up Syndicate, then skipping the rest of my classes to play for 10 solid hours, only breaking for caffeine and bathroom breaks.