I know this didn't come out this summer but I just Netflixed it a few weeks ago. As with the Clash of the Titans remake, what seems like a can't-lose setup (guy fights monsters!) quickly proves itself about as fun as playing with a wet, gray dishrag. And I don't choose that simile lightly; one of the constant fails of this movie is the bleached-out aspect of the visuals. I suppose it's meant to be gritty or something. The disappointment is thorough enough that I noticed it as it happened. "Gosh, there's Pegasus flying over a rocky landscape with some old Grecian buildings and it's all silhouetted agains the distant sun and YAWN how did they fuck this up so bad?"
Also, I am convinced that Sam Worthington is just NOT the guy; he will never truly occupy the A-list action niche which the key players in The Expendables created. I doubt we'll see much of him after the Avatar franchise has run its course (and we won't be actually seeing him in that anyway, ha ha).
The story should have stuck closer to the movie posters, more monster fight-y and less quest-y. And there's a lot of stuff in the movie that the trailers wisely ignored: the Russell Brand-like actor playing the "comic relief who redeems himself" son of Poseidon or the crappy CG cyclopses clumsily ruining an already tepid sweeping aerial shot of our heroes plodding through a forest. There are some decent monster scenes at the beginning and the end, so you may want to tune in for that. If you do, brace yourself for one of the most awkward, by-the-numbers ending kisses in the history of cinema.