Well, the 2000's can't come without the 80's. We're seeing old franchises making comebacks this generation (and good ones most of the time, just look at Bionic Commando)!
With that said, I favor the 80's for the pletora of SHMUPs that came out at the time (Gradius, R-Type, Darius, etc.). Oh, and also: Contra. Hehehe...!
Random game thought :
Why is Bionic Commando Rearmed 2 getting so much hate? We finally get a real game and they're not even satisfied... I'm starting to hate the gaming community so f****** much...