I Wouldn't judge Hercules just off the trailer. That being said, you still will probably want to have enjoyed the trailer.
Hercules is an odd movie, and takes a surprising tonal direction for an action movie that from the outset looks just like a CGI crapshoot. I'm not saying that everything in the movie works as it taken in a vacuum is solid but nothing special. They play heavily off the fact that you would expect Hercules and the Rock to have super powers, which he does of course but not to the extent you might expect.
Hercules plays heavily off the ideas that similar movies in the genre take. Things like gods and fate all are more or less mocked. It plays almost as a comedy but actually does a solid job with the physical action. While not exactly a Ridley Scott like epic the action is appropriately visceral. They don't use CGI to an extent that you get from the trailer, most of the action is practical effects with cgi just to pad out the large number of bodies. This, like the other aspects of the movie come in just short of being impressive. Thats ultimately the problem with Hercules there is some good ideas that clearly were thought out but the movie as a whole doesn't quite bring it fully on any front. The action is not as crazy or brutal as you might hope, and its not as comedic or dramatic to make up for that.
Primarily focused on a band of ragtag characters that seem striped right out of Thor. There is Thor (The Rock), the tough chick, the mystical man, the blond guy (his personality is different but they look the same) and others (fine it's not exactly the same). Among the group obviously the Dwayne "the Rock" the Johnson brings it in full giant pumped up force. While you might think his personality would be too upbeat for this role, don't worry the movie rightly changed around him as it should. Also the mystic has the best part of the movie with a pretty amusing running gag.
Considering Brett Ratner's last action movie X-Men 3 (I'm not dissing Brett Ratner Rush Hour is awesome) Hercules is pretty solid. He has a drive for action and comedy that has worked in the past well but here is just misses the mark. I'm pretty sure the only thing keeping this from being a five star movie is that the Rock had a torn pelvis during filming, don't worry though pelvis-less Rock is still puts the hammer down. (Sick Thor reference!)