[mGGDaedalus]

To make a less de-railing post than my last, I'll just say that Blizzard are good at making game engines with highly scaleable graphics. They allow their games to be played on a wide variety of specs while still allowing the flexibility in settings to look quite nice at higher settings. And really the ultra settings already look pretty nice, most of the extra features of something like the frostbite engine would be unwanted post-effects like lens flares etc (BF3 anyone?), which detract from the key principles of SC2 - ie being simple enough that you can always tell what's going on, without anything too distracting.