The thing that ruins grevious IMO is the fact he was SO much cooler in the original clone wars shorts. He wasn't a coward, he was a powerful General who was changing the tide of the war. Then in Sith he's kinda pathetic, I guess if they made him as cool as he was in the cartoon he'd take away from Anakin but still it just felt like such a waste of potential to me. Even back then I was extremely disappointed with him.
Eh... he does run, but then when he gets cornered he still gets pretty nasty doesn't he. Also he didn't start running from Obi-Wan until he pushed him against the ceiling, so

Seems to me like a guy who just knows the 1st rule of self-defense
Anyways, mine would be:
Chase sequences:
1) Pod race (the rhythm, the sound design - just ****ing piece of art).
2) Asteroid chase, close second (AWESOME blue bombs, other stuff's "just" cool though).
3) Feels slightly cartoony, but they have fun with the speeder sounds and it's still ****ing cool
Large scale battles:
1) Geonosis - once Yoda arrives. Not that the preceding phase isn't awesome, but we said no lightsabers, and it just doesn't compare to the ****ing ART unleashed once they fly into the desert.
Great rhythm, love the "chaotic shaky-cam" feel to it (nothing too fancy, just a little bit here and there) and how the ships growl towards and past the camera, the gritty visuals and the smoke and rockets owkjkrewlakjesvwtr
2) Sith opening, until the droid antics begin - great "punchline" right at the beginning, continued with stylish looks and an overall "grand" feel to it.
3) TPM space battle just had a great epic feel to it, minus childish Anakin; with an air of "despair" that wasn't quite there in Jedi (ironically so), and a powerful climax.
The undeniably moody supense intro aside, the gungan fight's obviously a joke overall
Non lightsaber fights:
1) Every "short burst of droid slicing" in I/III's respective opening sequences at the battle stations. Just so... concise. The droidekas bit from TPM and its superspeed punchline take the cake.
2) Jango Fett, nuff said. Cartoony CG Obi-Wan
somewhat takes away from it.
Haven't included Grievous - I like it, but not particularly as an action scene, moreso for the entertaining character bits.
Additional notes:
-hate, hate, hate the "droid factory" one. Yes, it's creative, looks and sounds cool, but boy does it feel cheap and unnecessary (and given the prequels, that's saying quite a bit). The schizophrenic score's unbelievably annoying, why didn't they keep the original one from the CD? RTZUIUERWZTPBXC
-cool robots vs. clones/wookies stuff around the middle of ROTS, but more of a canvas background and not particularly memorable; the whole dragon chase feels more like a part of that than anything that stands out. But let's all give honrary props to the "scorpion crawl" and "Grievous-wheel sliding down the slope" shots - creative as ****
