if i make the assumption that what you mean is that everything else is 100% perfect, and this one item is so bad it makes boardgames look epic, then i would have to go AI.
bad controls and bad camera just make a game really frustrating.
music really makes my game, i would never buy a game with bad, or worse no, music.
plot, characters and voice acting all kinda bundle together to create the immersion, plot is mos important, then voice acting, then characters, but any one of them being epicly bad would totally shatter the immersion.
graphics arnt a big thing for me, i can deal with low res graphics, and unsophisticated textures. but i cant deal with graphical glitches. clipping, artifacts, they kill a game for me.
Bad A.I. is the least of my concerns really. i dont mind an AI thats as thick as a brick, as long as the story and stuff are good, i can deal with hard mode being a walk in the park. if it goes totally the other way, and the game is just impossible to complete because the AI is too hard, i will bite the bullet and use cheats/trainers in order to see the end of the story.