RE4 is the game that KILLED the Resident Evil series for me, actually.
RE4 was a great game and a lot of fun, but it re-invented the formula SO much that it lost a lot of the flavor that made the original games great, in my opinion. I felt like the game was so action oriented that it lost all of the tension and scare-factor of the original games. Resident Evil has never been about run-and-gun action, and I really felt like that was what RE4 was all about. RE5 was much worse though. It was just a bad, bland action game through and through. Yuck.
For my money, the best Resident Evil game ever made was Resident Evil 2--that game just really had it all. The Gamecube REmake of Resident Evil 1 was also amazing, and is a close, CLOSE second. The RE1 Remake also gets my vote for the drop dead scariest RE game. Two words: Super Zombies. *shudder*