I respectfully disagree with both of you, I was incredibly impressed that they didn't trash it and it had actual merit. The camera angles, as Edge7 mentioned, were a bit meh a few times, but overall I was impressed.

As for not following the spirit of the game (taken from Wiki):

On the morning of a siege on a holy city, the Prince (seeking glory and honor) infiltrates the <del>Maharajah's treasure vaults to plunder the finest treasures for his father.</del> city so his brothers can conquer it. Upon defeating <del>rather inept guards,</del> some guy, the Prince <del>comes upon a mysterious chamber which houses</del> finds the famed Dagger of Time. Unaware of its power, <del>he climbs to retrieve the blade,</del> he is forced to flee the city etc etc, only to discover its abilities by accident. <del>Narrowly evading his demise, the Prince returns to his father, who plans to gift the hourglass (and the Sands of Time) to the sultan of Azad.</del> The Vizier (aka former king's brother) <del>suggests that the Prince unlock the hourglass so that the sultan might fully enjoy his gift.</del> wants the Hourglass of Time so he can become king in the past. The maharajah's daughter (who was captured during the siege), <del>Farah,</del> Tamina, tries in vain to <del>warn the Prince, who releases</del> take the dagger back to prevent the release of the Sands of Time.

etc etc. You can see the influences, imo, throughout the film. Some are harder to see though, so I can understand.