At least with Scream in the parking lot, it doesn't take up much room, Shockwave @ SFGAm took up a ton of parking lot space. Throw some grass in there at least!
My vote, however, goes to Mr Freeze at SFSTL. Inside it's got some color scheme thing going, but outside.. it's concrete. They couldn't even put in some stripes to fake us out to a parking lot theme! it's just lots of barren concrete! Crap!