Let me start by giving you the bottom line. If you loved 300, this movie is right up your alley. In fact, you might think it's the same movie. Scantily clad warriors doing battle against impossible odds, with gods in the mix and plenty of highly stylized violence ... sound familiar? It did to me, but I didn't really care because it was all so AWESOME!
Henry Cavill - who you may or may not remember as the jerkwad Humphrey from Stardust - takes the lead as Theseus and shows us why he's going to rock like a hurricane as Superman in the forthcoming Man of Steel. Mickey Rourke is the baddie, and Slumdog Millionaire's Frieda Pinto is the beautiful virgin oracle. John "Ollivander" Hurt plays a wise old man who is much more than he seems. And an actor named Luke Evans who I've never seen in a movie in my life, but he looks FOR ALL THE WORLD like Battlestar Galactica and Dollhouse star Tahmoh Penikett, plays Zeus (also, he'll soon be appearing as Bard the Bowman in The Hobbit). Oh, and one of the lesser known Cullens from the Twilight movies plays Poseidon. Stephen Dorff is in it, too.
The basic story is that the ruthless king Hyperion (Rourke) wants to declare war on the gods. To do this, he's going to release the Titans (who are not what you might think they are from seeing Clash of the Titans), and to do THAT he needs this special bow that was forged by Ares. Theseus, with the help of his fellow slaves and the lovely oracle, must lead the fight to stop him. Now, I'm a huge fan of Greek mythology, and while I was fine with the different way the gods were portrayed here, my one beef with the movie was that there wasn't more of them. Because when they finally join the fight, it is a beautiful, slow-motion-y, head-exploding thing to behold.
This movie was made by Tarsem Singh, whose first film was The Cell, which had a fairly forgettable story but a truly unforgettable visual aesthetic. I didn't see his later film, The Fall, but Immortals is cut very much from the same cloth as The Cell. The visuals are like nothing you've ever seen before, and even though it's not quite as coherent a movie as 300, I liked the look of it a bit more (notably, the color palette, which I found more pleasing to the eye than 300's nearly monochromatic look).
Like I said, if you dug 300, you will probably like this a lot. Yeah, it's essentially trash, but it's GLORIOUS trash. If you can find a theater that's showing this in 2D, I don't think it will lessen the experience at all. In fact, I think huge chunks of the movie aren't even in 3D anyway. (Though Frieda Pinto's naked bootay gets the up close, 3D treatment, if you're into that sort of thing.)