300 is like a replay of the world's most violent computer game on steroids and speed. It is a rather simple story of glory, courage and the fight for freedom with a bit of betrayal in the mix.
Everything is completely exaggerated so the images looks like the comic book it is based upon. It may not exactly be historically correct or the least bit realistic. It may even be a bit monotonous at times. But it can't be argued that the fighting scenes are very impressive and there are plenty of hilarious one-lines with a humor as dark as a black hole.
The ultra skilled Spartan soldiers are super men and pure fighting machines that spit in the face of death. The Persian enemy is an overwhelming army of soldiers, slaves and monsters that look like they marched right out of hell. Of course all these men get to look a bit ridiculous because they all wear sandals which subtracts about 50% from their tough look so maybe somebody should have told them that real men don't wear sandals. Not going to a battle to the death and not at all.
If you want to see a movie that has cascades of blood and limbs and heads chopped off in multiple ways I think you will enjoy this Zack Snyder movie.