Why you SHOULD NOT watch it:

1. Promising, that's it.
2. God of War is WAY better (of course).
3. Poor story telling and script: A trade-off for parading abs? Maybe they thought that Henry Cavill's six pack would suffice and words coming out of his mouth would ruin it. The part where he rallies off the soldiers at the Hellenic gate reminded me of Brad Pitt in Troy. The posh UK accent didn't do much either.
4. Only five of the Olympian Gods were shown. I was really hoping for more. In any movie that casts them, it really makes me curious as to how they will be presented. 
5. Weak and inconsistent story:

a. The bow was so hyped-up in the beginning only to be used (as far as I remember) in three scenes (1. Theseus killed the soldiers in the village 2. King Hyperion shot the Hellenic gate 3. King Hyperion shot the cage where the Titans are).

b. The Titans were ravaging-human-like-monkeys covered with ash. I thought they were supposed to look a lot like the Gods and also match their powers. 

c. God versus Titan fight scene: I understand that these are Gods we're talking about and the fight scene was kind of great but towards the end of their fight, Zeus went on top of the cage, placed his helmet down, pulled some chains and made the mountain collapse on them, I thought everyone inside would die. Next thing you see, he's carrying Athena and the Titans were rushing to get to them but before they could, the two "teleported" back to the clouds. They could have done that from the beginning!

d. Ares (God of War) helped Theseus when they were about to be slaughtered by the enemies even if it meant his death. As far as I know, Ares is supposed to LOVE anything and everything about a war. Why would he do as much as help a mortal to stop an epic battle (God versus Titans)?

More reviews at rottentomatoes.