I've never seen the 1981 original version of Clash of the Titans. I wasn't originally planning on seeing this new updated version either. Going by the previews, this looked like nothing more than a CGI-fest...which is what it pretty much ended up being. To quote Sam Worthington from various interviews, it's basically him "in a skirt with a rubber sword, killing monsters". If you're expecting anything more than that, then yes, you will probably be disappointed.
Some of the cast manage to make the most of what they're given to work with. Having not seen Sam Worthington in anything prior to this film (except Terminator Salvation), I don't really have anything to compare his acting to. He was good in Terminator Salvation and he's good in this as well (despite the occasional slip-up of his accent). He serves his purpose as Perseus, playing the action hero well enough. His interaction with the humans who accompany him on his journey is probably the most entertaining part of the film. Mads Mikkelsen, who was a memorable villain in Casino Royale, actually gets to play a fairly decent good guy in this film (Draco). Sure, it's the role of the typical grumpy guy (who's reluctant to follow the "saviour" and is a bit of a bully) teaching the hero how to fight and who eventually comes around to respecting the hero and ending up on good terms with him...but Mads manages to make his role a bit more than a cardboard cutout, thankfully. The other men who accompany Perseus aren't too bad either (they do provide a bit of humour), but they're not given much character development at all. Actually, there's very little development for any of the characters.
As far as the gods are concerned, they're basically just a bunch of folk who stand around in Cloud City (I mean Olympus) and talk. Liam Neeson isn't given a whole lot to work with as Zeus (shining in his silver armour as brightly as Marlon Brando did in the original Superman movie wearing his tinfoil costume). Ralph Fiennes, while good, is kind of irritating with his raspy voice as Hades (though, thankfully, that goes away by the end). The rest of the gods have jack squat to do or say.
I really didn't like Jason Flemyng's satyr character. Alexa Davalos pretty much just plays the damsel in distress in the movie and leaves very little impression as Andromeda. Gemma Arterton (as Io), however, proves to be the most successful female character in the movie. As a sort of angel on Perseus's shoulder, she guides him, teaches him and actually proves *useful*. Her and Worthington work well together/have good chemistry and I enjoyed watching the two of them share scenes. I was happy with how they ended up in the film.
As for the FX, the previews basically give it all away (Clash of the CGI might have been more befitting a title for the film). Perseus fights giant scorpions, Perseus fights the Kraken and Perseus fights Medusa. As large-scale as the Kraken was, I personally enjoyed Medusa more. The fight with her proved to be the most interesting of the many fights in the film. I liked the 'look'/design for her and I also really enjoyed Pegasus, the flying horse.
I'll just come right out and say it: the movie has many a flaw. The story isn't great, the pace is off, the writing is slapdash and most of the dialogue is sketchy at best. While the movie does try to get across a message, it comes through in a somewhat haphazard sort of way. Having said that, if you go into this film not expecting much more than a Monster Mash of the Titans...then hopefully it should prove to be entertaining enough.
Crap of the Titans? Not quite. But at the same time, it's kind of forgettable. As Worthington describes it, it's a "popcorn flick". Take from that what you will.