The best thing about R1 was the alt-history setting. R2 all but threw that away. Aside from the occasional background prop (e.g. old cars parked on the road) there was very little to remind you that you were in the past.

Your fellow soldiers also flew around in spaceships as if they were current technology. Made the game feel more like Halo than the WW2-era-alien-invasion of R1.