Dude, a lot of these suggestions are just plain weird. Alexander and Reign of Fire? And dude, Crash? What a mediocre film... Kurosawa, though. That's cool stuff.
Anyway, quality films:
-In a genre full of dumbed-down films, LEON THE PROFESSIONAL is better than sex. Gary Oldman turns in an awesome, over-the-top performance, Jean Reno is perfect, and even Natalie Portman shines (have to get used to her a little bit, though). Nice directing throughout, only one bad shot, and it doesn't ruin anything. There's a lot of very cool, very subtle stuff to enjoy, and a lot of very cool, very not-subtle-at-all stuff to enjoy. Like, y'know, the action.
-If camera-work means anything to you, watch CHILDREN OF MEN. Totally took me by surprise when I went to go check it out. Five-star film for sure.
-THE GOOD, THE BAD, AND THE UGLY is possibly one of the best movies ever filmed. The peak of Sergio Leone's style (and it is a sexy style).
-THE PRINCESS BRIDE might by *the* best movie ever filmed. If you don't like it, you probably don't get it...
-THE THING and BIG TROUBLE IN LITTLE CHINA by John Carpenter are both ridiculous and fun.
-Horror-wise, THE DESCENT is by the guy who did DOG SOLDIERS, and both are decent, unpretentious horror films (THE DESCENT is the better of the two). The first two ALIEN movies (by Scott and Cameron, respectively) are great sci fi/horror (the second one is more more sci fi/action, really).
-You wanna laugh, throw up, gasp, and hate yourself: OLD BOY. Sickly beautiful. I hear SYMPATHY FOR MR. VENGEANCE does something similar, but I haven't seen it.
-As for war movies, the best of the best are APOCALYPSE NOW and BLACK HAWK DOWN. I imagine you've probably seen those by now, though, if you like the genre, as they aren't exactly obscure.
-Tarantino's best was PULP FICTION. RESERVOIR DOGS is probably worth a view, but it feels almost like a play. KILL BILL is sort of humorously fun.
-Movies that have come out recently... well, I'd rent THE DEPARTED and CASINO ROYALE. Skip PAN'S LABYRINTH (pretty visuals but no substance, incredibly overrated; the translation really played havoc with it). If you don't take it seriously, and if you're a guy, you'll enjoy 300, which is in theaters at the moment.
Ayup.