I prefer atmosphere. The closest thing on that list would probably be music, actually, but I don't want to put that because atmosphere is really a combination of a lot of things. It takes visuals, music, and plot situation to nail down right.
Take the introductory bathosphere ride in Bioshock, for instance. That relies on the contextual situation, the music, the visuals, the character of Andrew Ryan, the dialogue and its contrast to the visuals. All of those things create an atmosphere (or hydrosphere, in this particular case). But that atmosphere is absolutely key for the player. It makes and breaks games. It determines what kind of game it really is. Timesplitters was rather cartoonish with its atmosphere - consequently, the game was meant to be more comedic than other shooters. Metro 2033 had a suffocating atmosphere (quite literally, actually), and consequently, even the gunplay seems heavy. It was an amazing game regardless. On a side note, the game is about 10x as awesome in Russian with English subtitles, which is a menu option that honestly should be default, or at least, the gamer should be provided with a clear choice upon starting a new game concerning the language, a la Lost Odyssey. The Russian simply adds so much to the feel of the game, making it feel like an Eastern European title instead of an odd Western/Eastern cross.
But anyway, my answer goes to atmosphere, and I would love to see a reviewer that puts that as a separate category or rating.