8.
I first played it on PS2, so my experience included all the improvements that came with that version.
I found it very replayable with the unlockable and everything, and I loved the silly playthroughs with Leon using an infinite ammo Tommy Gun, and Ashley in a fuckin suit of armor. Just hilarious.
The proverbial shark jump happened in 5; 4 was a great mix of kitch and horror, while 5+ went way too far down the action lane. There's nothing to be scared of when you have watermelon arms, lookin at you, Chris.