300 is the best movie I've seen in quite a while. How can you not like a movie with heroic warriors making a last stand against impossible odds? They fight knowing that they will all die. They fight because that is what they were bred to do and no one else will. If they fall too early, their homelands will be ravaged. It is a challenge like no other; stay alive, kill everything in your path, give your last dying breath for freedom.
On top of that you get multiple beheadings, Matrix-like fight scenes with severed limbs a flying, and spouts of blood that would make Monty Python blush. What's not to like?