Admittedly, it's a bit of a tall order to make a trailer for a movie whose premise is still far from clear. The first half is kinda cool, but it doesn't really have much to do with what little is known of Avatar's story, which I think is set a couple centuries in the future. The second half is just sort of so-so. Not terrible, but there's definitely better out there.
And this is one of them. This probably impresses me more than it necessarily should because I've seen so few of the movies used to construct the trailer, which according to its maker include City of Lost Children, Sky Captain and the World of Tomorrow, Casshern, Dark City, Cast Away, Aliens of the Deep, I, Robot, Silent Hill, and AI: Artificial Intelligence. Of those, I'm somewhat ashamed to say I only recognized Laurence Olivier from Sky Captain (though I have seen Dark City). Part of the reason this trailer works fairly well is its creator chose movies that are reasonably similar stylistically, making it more difficult to figure out what does and doesn't fit together if you haven't seen the source material (we'll soon deal with a trailer that just throws together a bunch of famous contemporary movies).
Captain America (2010)
This one is a bit different from the rest, as it's a completely original trailer instead of a fan mash-up. It's surprisingly intense for what is ultimately a bunch of dudes running around on a beach, some of whom are very clearly wearing sneakers. Still, the pounding music and washed-out look do have their charms, and remembering to throw in a shot of Nick Fury is a definite plus.
Cowboy Bebop (TBD)
This one has to get points for sheer insanity. This combines one of the Matrix sequels, The Phantom Menace, Wanted, Live Free or Die Hard, Firefly, Constantine, and Deep Impact, and those are just the ones I can easily identify. There's some definite overuse of Angelina Jolie here (should you really include the curving of the bullet when that's so closely identified with Wanted?), but it's certainly never boring. Cutting all the dialogue was also a good call, as forcing the characters to say things that aren't immediately recognizable from previous movies is usually the biggest pitfall of fake trailers. From what I've seen, there's just no good way to do it, and unless you've got something to distract the viewer (like Brad Pitt in full Thundercat makeup, for example), it can be fatally distracting.
Ghostbusters 3 (TBD)
Wow, five minutes is a long time for a fake trailer. Still pretty good though. Here, as the creator puts it, is the "recipe" for this trailer:
Ghostbusters, Ghostbusters 2, Predator, Independence Day, Casper, Nightwatch, Gremlins 2, Lost in Translation, End of Days, Haunted Mansion, Hellboy, Earth vs the Spider, Orange County, Blues Brothers 2000, Miss Congeniality 2, Christmas with the Kranks, Miss Congeniality, Sleepy Hollow, X-Men, The Blob, Spider-man 3, High Spirits, Frighteners, Constantine, Mars Attacks, Charlie's Angels, Be Kind Rewind, Honey, We Shrunk Ourselves, Dan in Real Life
Makes that Cowboy Bebop trailer look positively unambitious. At least this one manages to be somewhat deft about including clips from Lost in Translation. One of the less impressive trailers I saw just came right out and explicitly made Dr. Venkman an actor now...and that's just nutty. Although after spending so much time with the original cast was there really any reason to throw in a bunch of new Ghostbusters at the end?
Green Lantern (2010)
I'm a bit torn about this one. There's something a bit perverse about using quite so much footage from a Marvel movie for a DC trailer, and it was probably an overstep to actually use some of Johnny Storm's dialogue from Fantastic Four: Rise of the Silver Surfer. Still, I'm being more than a little nitpicky, as this trailer features some truly awesome digital trickery to actually create some footage of Green Lanterns flying, and the casting choices of Tim Curry as Sinestro and Warwick Davies as a Guardian are inspired. Although if Denzel Washington is supposed to be John Stewart, I'm sorry, but I'm just not buying it, at least not on the strength of two random clips.
Iron Man 2 (2010)
I'll assume this was made before Terrence Howard was mysteriously removed from the sequel in favor of Don Cheadle. Cutting in footage from the Iron Man video game was, to put it mildly, a mistake, because it just doesn't gel properly with the rest of what's in there. I will give it credit for some clever cuts that sort of do make it look like Iron Man and War Machine are sharing the screen, but using "Iron Man" as the trailer's main song? I feel as though the end credits to the first movie pretty much retired the use of that song.
Spider-Man 4 (TBD)
Some terrible music choices shouldn't necessarily take away from the technical merit on display in this trailer. It's certainly a lot more interesting to try to spotlight the Lizard as the Spider-Man 4 villain instead of, say, Venom again, which pretty much involves remixing a Spider-Man 3 trailer. Or you can use Carnage, which is basically the same process, except you slap a red filter on it to make it look a bit different (though this trailer includes him through clips from Resident Evil: Apocalypse). I don't know whether I would have relied quite so much on Jurassic Park, but I guess where else are you going to find so many shots lizard-like things in laboratory settings?
Overall, I'm not sure any of these are mindblowingly awesome in quite the same way that the Thundercats trailer was, but credit where credit is due - some of these are pretty cool, assuming your suspension of disbelief is ready to work overtime.