I am a big geek, and I know it. One thing we big geeks like is COOL ACTION SEQUENCES. These are a totally misunderstood phenomina by the general masses. In fact, these are often misunderstood by directors, cartoonists, storyboarders, etc.
An action sequence isn't just how cool it looks. Sure, aesthetics are important. But the real importance is (ah, me, another theory) "Threat". It's obvious, when you think about it. An action sequence is as cool as the amount of danger and force involved. Think about all the cool sequences you've seen. Cars spinning wildly, partially out of control, slamming into other cars, exploding. Jedi hurling things around the room, cutting things in pieces. Wading hip-deep in Agents, knocking them away, crushing them down, hurling them aside. Performing incredibly fast and skilled martial arts, always one step ahead of the other men with weapons.
If there's no feeling of threat, there's no feeling AT ALL. Threat is the ONLY thing that matters in a fight - threats and dealing with them. There are a nearly infinite number of ways to put threat into a fight or action sequence, but the IMPORTANT thing to remember is that THE AUDIENCE HAS TO KNOW IT'S THREATENING. (And, by the way, the audience will automatically empathize with the threatened.)
When you're dealing with humans, cars, or other common stuff, that's usually pretty easy. The audience has a baseline. They know roughly what a human or a car can take and is capable of, so if someone suddenly whips out a crowbar or a gun, there is a DEFINITE threat. A way to inject this into EVERY fight is to make EVERYTHING have a MASS, even lasers. Everything SLAMS around, flexes, rebounds, dents, blasts, has a hard time stopping. The audience can feel the threat inherent in a heavy, fast-moving object.
The problem is when you reach the bizarre stuff. Star Wars and Star Trek are prime, obvious examples of these kinds of fights. The audience has NO IDEA how much or how little threat a given thing is. Is a blaster threatening? A phaser? How durable is a cruiser?
The way they resolve this is by setting up a THREAT BASELINE. Which they do by showing the full effect of a threat. They show the photon torpedo HORRIBLY MAIMING a ship (often the main ship, before its shields go up). Suddenly, we know how much of a threat a photon torpedo is. They show a blaster being used against someone, and that someone dying. Suddenly, a blaster is a threat. A light saber cuts off someone's hand. Suddenly, the lightning-fast fighting is a HUGE threat, because we know how much damage those things can do.
You have to ESTABLISH THREAT in your action sequences. If your source of threat is a bit odd, like laser weapons or giant squid, you have to establish them as a clear danger before you can start using them in an action sequence.
The other misunderstood thing about action sequences is that they aren't just pyrokinetic displays to tweak my testosterone. An action sequence, whether a fight or a chase or a series of banking transactions, is nothing more or less than a chance to explore and revel in a character (even if that character is a giant starship). A good action sequence isn't just wham-blam-thank-you-maam!
Take a look at classic action scenes. Most of them involve reversals, tight spots, and persevering when injured. These things serve to both explore a character - by showing us how he acts under pressure - and revel in a character - by showing us what he is capable of. They're the same basic character-driven font of joy, and NO action sequence should be without them.
I would think this to be obvious. I don't know why so many people SCREW IT UP.