immersion.
all the listed elements contribute to it, but its how they work together that really counts. as with all artistic mediums i suppose, im looking for something that can draw me into the story/setting/whatever and get me interested about what happens in it; or for video games, what i can do in it.
sandboxes like morrowind/oblivion, RPGs like baldur's gate and planescape torment (which ive only recently discovered to be AWESOME); even a good game of civilization against a competent AI. these are the kinds of games i enjoy the most, because every aspect of the game, from the gameplay to the aesthetic to the narrative to the damn loading screens all fit together and contribute to a unified tone and pace that i cant help but get sucked into.
sure i enjoy other games (super smash bros is maybe my favorite multiplayer game ever, and one of few that i actually enjoy), but im primarily looking for the same thing in games as i do with films or comics or books or music; something that can draw me into whatever fantastical experience it has to offer and make the experience interesting.