RE4 b/c I'm playing it currently and loving every moment of it. Escourting Ashley should be a pain in the ass, but it kinda isn't. You don't accidently shoot her b/c she ducks if you point your gun at her. O yeah bosses = bad ass
RE2 b/c it was the first RE that gave me a little scare when I played through the latter stages of the game. Plus it had awsome replay value b/c you could play as Leon or Claire or even the extra chars. they had.