I voted RE1 (the Gamecube remake, mind you). First time through, sweaty palms almost guaranteed. I also really enjoyed speedrunning it after several playthroughs.
Yeah, I'm not surprised RE4 is really popular. I've played the shit out of it as well, but it's hardly scary. You are literally a one man army. And the story? Are you bad enough to save the president's daughter? The game has that B-movie vibe and it's not afraid to show that it doesn't take itself seriously.
For me, Resident Evil ended with the nuclear destruction of Raccoon City at the end of RE3. Wesker is still alive, Umbrella still exists. No BSAA bullcrap.
If I had the chance, I'd reboot the franchise at that point attributing 4, 5 and 6 to the feverish nightmares of Chris and Leon, whose psyches obviously took a beating. And since Leon is the one with imagination (and probably still a virgin at the end of RE2), he's the one with the weirdest dream (4). Chris just doesn't really like people of colour unless they're hot women. And RE6, well, that's just Chris and Leon together getting high on a long evening/ night.
Ahh, one is free to dream. Capcom, however, is free to continue driving the franchise further into the ground. How long till it hits lava?