Though I like both series, SH gets the nod from me. Unlike RE, the SH series is scary. More than that, the fear factor holds up even after repeated playthroughs. Heck, the original SH still managed to scare me while I watched a friend play it and had already beaten it 7 times myself. Considering I've never seen another game or movie that can get any more out of me than the usual surprise at something jumping out at you reaction, that's saying something. When it comes to horror games, SH sets the standard that other games wish they could match, and RE seems to have given up on trying to match.
As for RE4, I honestly have to say that it's the weakest game in the series (with the exception of the original PSX RE) as far as I'm concerned. The action became extremely repetitive, and the game dragged on waaayyy too long. It should have been half the length it was at most as far as I'm concerned. I had stopped playing altogether for the better part of nine months or so before forcing myself to finish it, mostly for the sake of finishing it, and partly in the hopes it would improve. Unfortunately it didn't. Looking back, my time would have been better spent beating some of the other games I hadn't gotten around to finishing at the time. I don't plan on ever playing through the entire game again, and it's got me seriously questioning whther any future entries in the series will be worth my money. Keep in mind, I'm not someone who hates RE4 simply because it was different. I applaud Capcom's attempt to breathe some fresh air into the series and do think there were plenty of things that needed changes and improvements from the old games, but RE4 just bored me to tears.