God I love David Mamet
No one makes movies like this. You cannot get 10 minutes into the movie without knowing it's a Mamet because of the dialogue and acting.
No other director cares this much about making dialogue sound like it sounds in real life. I see so many criticisms that the dialogue in Spartan is bad or the script is bad. The truth is that Mamet directs his cast to speak as realistically as I've ever seen since Ridley Scott's Alien.
Now, it's not perfect. People don't repeat themselves as plainly as Mamet has his actors. But it's that much more realistic than we usually get to see. Most movies today contain seamless bantering with no obscure or unclear lines. It's refreshing to see someone take a different approach.
Mamet is the only director with a signature that makes his movies worth watching completely ignoring the plot.