Which Series Scared you the most? For me Silent Hill wins hands down i remember being very young and not touching the game for months becuase it was just too much. Resident Evil was Awesome i Couldnt put it down but it wasn't as bad.
Silent Hill (I'm biased), although I don't think it is actually that scary (except the more modern games, but not for the right reasons). Disturbing though. And awesome. Clock Tower, Siren, or games like that might be scarier. I'm not as familiar with those though. Checked out 1 or 2 of them before.
silent hill 2 was the shizzle i got an erotic boner fro tha rap scene with pyramid head and a zombie if you watch be prepared... <iframe width="420" height="315" src="http://www.youtube.com/embed/aHxd0TCSzdE" frameborder="0" allowfullscreen></iframe>