What features in games just pull you in? What do you hear about, and think: "Yes. That's what I like. That's what I want"
1. For me, it'd definitely have to be a level editor. That's why it hurts that I don't have Little Big Planet yet... (Examples: Little Big Planet, N+, Megaman: Powered Up)
2. Also, for me, it's really awesome if a game is promoting an original idea (the first Guitar Hero game, Mirror's Edge, Katamari Damacy, Kirby: Canvas Curse)
3. ...If the game has a cool style (The World Ends With You, Katamari Damacy, Okami, No More Heroes)
4. And lastly, this isn't TOO important for me, since I already have games that fill this requirement, but I really like it when I can get good at a game that allows me to "Show off", so to speak (Dance Dance Revolution, Drummania, Rock Band)
Of course, these are just things that add to the experience, and the real fun comes from the overall value of the game, right? Right.