Even the academy had the fucking brains to not nominate Revenge of the Sith, but whatever. Kong's visuals were really impressive, although War of the Worlds' effects were more realistic.
I thought Kong cut the most corners of ANY major release with SFX this past year. I don't see how you don't give Sith some love here.
I think because Star Wars uses effects to the point that they're almost not special anymore. Coming close to the reason why Pixar animated films arent nominated for Visual Effects - because although exceptional, they exist in an entirely synthetic world. In this regard I would suggest that Episode III did a much better job than Sin City but of course thats ILM for you.
Personally, I like to guage the effects on their integration with real footage and the degree of innovation. Both King Kong and War of the Worlds were exceptional in these departments. With King Kongs digital set extensions and the lead motion capture performance. And with War of the Worlds' level of destruction and innovations allowing Spielberg to pull off graceful shots like the one on the highway.
As for Kong cutting corners, thats slightly unfair given how bloated the thing was. Lets face it - the only weak part of the film (effects wise) was the brontosaurus chase. Alright, the dinosaurs werent always on par with Jurassic Park but like Batman Begins effects that film had the benefit of featuring them in darkness. I should see it on DVD though.