1. Good gameplay. Kinda don't wanna elaborate on this because this post would be pages long but yeah. It works like this, at least for me: gameplay > story >graphicsHamst3r has a Dead Space 2 playthrough, so if you're into horror games you should check that out.
And naw, DP wasn't a good game. It was a good and funny story but there are more entertaining ways to pass time.
2. Our fine bro hamst3r: http://www.youtube.com/hamsteralliance and http://www.youtube.com/nanosuitninja if you feel like getting your crysis skillz dissed.
For me a good horror game is composed of great pacing and backdrop. It doesn't have to have many scares, if the games shakes your frailty hard during the playthrough.