I think Game-play and Game physics are still two important factors in the success of the game.
I still have not found a game with a physics as good as the Half Life 2, it still looks beautiful.
Fear, When I played it, it really took me by surprise as I never thought a game could really scare me even a bit, but it did.
Games with absolute focus on the gameplay like Bejweled or Plants vs Zombies etc still keeps the player stick to the screen for hours and hours.
I agree that games have already hit a saturation point as far as the graphics is concerned, so adding better physics , mechanics and better destruction explosions, character modelling could move current generations game a bit farther.
Half Life 2 had good texture facial movements and the best physics to date in FPS, Fear had a pretty decent AI and immersion level, Mass Effect 2 and COD MW/2 were awesome in graphics and could still run on normal systems.
I don't think so graphics can provide good level of immersion if you have less elements in the game. Good physics, gameplay and elements in the game are must.
DX 11, well atleast for now I wont be missing it at all I can still play games with same fun and graphic depth as with a DX 9.