Resident Evil used to be the same category as Silent Hill when both started out: survival horror. However, Resident Evil has evolved into a mutant hack and slash fest that digresses from the previous genre. Silent Hill has become a series that lost its charms after the first few games, however the fourth one did perk my interest.
In terms of scariness: Silent Hill
In terms of gameplay: Resident Evil
In terms of replayability: Resident Evil
In terms of music: Silent Hill
Best RE: 4
Best SH: 4, again.
Verdict: Personally, I like a game where I feel empowered, not helpless. And Resident Evil tends to that. But if I ever need a game to have me stuffting my jeans, wishing I hadn't used those bullets, then Silent Hill. Overall, Resident Evil is better (despite capcom slowly killing it :((()