Michael Crichton (RIP) novel and Steven Spielberg film: Jurassic Park.
I generally list Jurassic Park first among the major influences of my life, and put it at or near the top of lists of favorite books and movies. My dad read me a parentally-edited version of the book when I was three or four, and my parents took me to the movie when it was released in '93. I don't remember it specifically, but Dad's version of the story has me standing on my seat saying, "This wasn't how it was in the book." Apparently I haven't changed much.
Now it's entirely possible that the Jurassic Park's significance for me comes from permanently burning it into my physique by seeing the movie and reading the book more times than I can count and has nothing to do with any qualities of the original work. It's possible, but I don't seem to be only person who appreciates it.
Whatever the reason, these are some of the features of Jurassic Park that stand out to me. There certainly repeated elsewhere, and something else might have done it first, but I they're things I associate with it, and things I think it does well.
"Life finds a way"
Avatar may have been the ultimate environmentalist film (potentially marred by the recycling of all those 3D glasses), but a lot of those themes showed up in Jurassic Park, as in that Ian Malcolm quote. Possibly, this is why I was able to stand Avatar. The thing I liked about Jurassic Park was that the themes appeared more subtly. It doesn't make cutting down trees and strip-mining into plot points. Actually, the theme of the power of nature exists more strongly in the film version than it does in the book. Crichton's novel focus on chaos. He even uses the name Murphy to point to Murphy's Law. Anything that can go wrong, will go wrong. The dinosaurs are that thing, but the fact that they're living animals isn't really considered. His novel Prey dealt with a similar situation involving nanobots, so it doesn't seem it was a theme he was interested in.
Spielberg and screenwriter David Koepp on the other hand, seem very interested in playing up this theme. Notice that no human kills a dinosaur in the movie? In fact, it gets summed up when you look at how the scene where Muldoon hunts raptors is translated from book to film. In the novel, Muldoon literally goes out with a bazooka and blows several raptors apart before running out of ammo and having to take shelter (and Muldoon survives and escapes the island). So basically, the weapon technology and dinosaurs go head-to-head and end in a stalemate. In the film, Muldoon stalks the raptor, but is outsmarted and killed ("Clever girl" is still one of the greatest lines ever). Nature wins. Call me crazy, but I prefer this to a magical forest god. The Lost World film went the Avatar route with corporate strip-miners and a heroic Greenpeace saboteur. I think that's one of the flaws of that movie (though I still like it).
Ensemble of characters
Jurassic Park doesn't really have a single main character or hero. Okay, sure Grant is in a lot of ways, but the story doesn't revolve around him or spend all its time focused on him, like Avatar revolves around Jake Sully. I've noticed that a lot of my favorite stories work like this (The Lord of the Rings is a prime example). I think it's because if a story has one hero, too much of my enjoyment of the film will be based on how much I personally like or relate to that character. In a story with a large ensemble, this problem goes away, because: (a) There's a good chance I'll like someone, and (b) the story and events drive the narrative and so I want to find out what happens, even if I don't care too much about any of the characters. That's not to say I like stories where none of the characters seems to important. I know a lot of people love G.R.R. Martin's Game of Thrones series, but I just couldn't get into it with the way he kept knocking off characters.
I'm aware that my love of the superhero genre seems to fly in the face of this, but let me point out that one of the things I liked about Iron Man 2 was the inclusion of Black Widow and War Machine, making it more than a one-man show. Basically, this is why I'm psyched to see The Avengers. Jurassic Park may have been what taught me to love stories with a team where everyone has their own specialty and role. Of course, this can be incredibly dangerous for a writer, as its only one step away from paint-by-numbers characters and you run the risk of ending up with "token" characters. Still, I think it worked out in Jurassic Park, and when team stories work, they are my favorite.
Real science fiction
As far as I'm concerned, Jurassic Park is a great example of hard science fiction. I once read a book called The Science of Jurassic Park and The Lost World and my conclusion was that the science presented in the story wasn't so much impossible as it was impractical (it wasn't that it was impossible to get dinosaur DNA from amber, it was just very unlikely). This is a far cry from Star Trek-style science fiction with Tachyons and M-Class planets. I love me some good space opera, but I do think there's a value in science fiction that actually is based in possibility. There's really two kinds of science fiction: the kind that reflects on science and the kind that comments on culture. Jurassic Park belongs in the first group, and I think its one of the better examples of it.
Dinosaurs and Jeeps
It's my opinion that there is a correlation between how much I like a story and the amount of cool stuff in that story. It's not a direct correlation, just throwing in a bunch of cool things won't make something good (see: Spider-Man 3). However, a T-Rex trashing the tour vehicles and chasing a Jeep Wrangler is pretty much awesome. And the aforementioned scene with Muldoon hunting velociraptors is a great action sequence whether Muldoon has a bazooka or a SPAS-12. And thanks to Jurassic Park, I've learned what both those weapons are and have a long-standing obsession with Jeeps. It's my personal philosophy that if an author decides he or she going to include something like dinosaurs, than that author has the responsibility to make those dinosaurs do something awesome.
This almost seems to go against the previous point, but to paraphrase Ian Malcolm, just because you can do something doesn't mean that you should. To put that in other words, just because Jurassic Park III could show a Spinosaur fighting a T-Rex didn't mean that it should have. It's the phenomenon that's taken over much of Hollywood with the CGI-fests that take over the cinema every summer. I like those movies, but they tend to sacrifice story for visual spectacle, and that's not necessary. I think this is the real difference between the Star Wars original trilogy and prequels. The first time around, George Lucas couldn't afford to have an army of Gungans fight an army of Battle Droids. Similarly, Jaws is terrifying because you don't see the shark. Sometimes, restrictions on what can actually be shown force the writer or filmmaker to tell a better story.
And there you have it. Jurassic Park. One of my top movies (and books) of all time, and certainly one of my major influences as a writer.