Resident Evil 2
Resident Evil 2 is our favourite of the original games. It struck the perfect balance between action and puzzles, the first game having too much of the latter and the third game the former.
It refined the original, added new weapons, new characters, and a new setting in the form of a massive police station. There was even a massive improvement made to the notoriously awful/awesome (delete as you see fit) voice acting.
We still remember the opening dash through the streets and back alleys of Raccoon City to reach the police station, all the while plugging moaning zombies with our crappy pistol, as if we played it only yesterday. There's no denying the brilliance of Resi 4, but it wasn't technically a zombie game anymore, and Resident Evil 5 just lost the scares completely.
Resident Evil 2 is the classic that catapulted the series in to the gaming zenith, and if you look past the awkward tank controls and badly aged visuals, it's still a heck of a lot of fun to play.