Another strong year for movies, but if you know me, you already know my pick. There can only be one answer.
Heat

Michael Mann's masterpiece crime saga set out over L.A. Everything Mann had learned about writing and directing up to this point culminates into a genius work of art.
Heat started out as a potential TV show from 1989. The rejected pilot was rejected and sold as 'L.A. Takedown'. Mann spent 4 years after that re-writing his script and re-working things. Detective Vincent Hanna would become Lt. Hanna, and he would write a whole crew of cops under him. Same for Neil and the bank robbers.
I've talked about Heat for many years. It's one of my favorite movies and was something that made me want to write. Mann's attention to detail cannot be overstated.
The failed heist scene has so many little details. Watch how Pacino and DeNiro look at each other through the surveillance camera, feeling each other's presence. Even though he can't see him, DeNiro knows someone is there watching him from a gut instinct. Then the cut to the crew outside on the rooftop and where the camera drops, showing their point of view.
Heat has the greatest shootout scene in cinema history.
When Val Kilmer passed away a few months ago, this was my first thought. Look at this scene of him going all iceman. Kilmer's reload time here was so fast that this clip was used in marine training at Fort Bragg.
This is what happens when you hire capable actors and spend the money putting them through training to do the stunts you need them to do.
Note: This scene with the bank robbery has been redone so many times in GTA games. Both in GTA IV and V they did a heist based on it. The bank robbery in Vice City was partially inspired by it. GTA V also had a heist with the garbage truck from the intro of the movie. I can make so many examples of how this one film inspired so much stuff, but I like to focus on the writing and characters.
A case on how strongly written of a movie Heat is,
is this blog. Someone went through and carefully examined how well written every character is, excluding the 3 stars on the poster. Every character was believable and you can imagine them doing things after the movie's events. Note how the blog writer came to the conclusion the secondary villain Van Zant is straight out of Miami Vice.
Long story short, Heat is an absolute classic masterpiece that deserves every bit of praise it gets. If you've never seen it, you're missing out.