This movie was actually great. You begin your review with some accurate points, listing aspects of the production that were excellent, but your review hinges on your opinion that the story is terrible.
You're wrong.
If your idea of Robin Hood were informed by more than just Errol Flynn, Kevin Costner, and Carey Elwes, (Edit: and Disney, and Loony Tunes) you might get it. If you had ever read "The Merry Adventures of Robin Hood" you might have a better perspective. Hell, if you even had some understanding of English history, you'd be better off. Sadly, you seem to want another kid's movie.
The legends of Robin Hood are not kiddie tales for bed time. Sure, American movies have adapted them for that, but they're not originally silly at all. You and many other reviewers, however, seem unable to deal with seeing a Robin Hood movie for adults, and that's a real shame.
This movie is made for intelligent adults. It acknowledges that during this time period in England, Freemasonry was invented, King John was forced to sign the Magna Carta, Richard had bankrupted the country to finance a series of Crusades, and there were lingering tensions between Saxons and Normans. The story of Robin Hood is not the story of a man, it is the story of a country - England - and this movie tells that story.
If you want to see a debonair fellow in green tights crack jokes and sing "hey nonny nonny," somehow remaining immaculately clean and well groomed while living in a forest, this is not your movie. If you want to see a kid's movie, this isn't it. If you want to see a beautiful movie that captures some of the truth of 13th century England (even while taking liberties with a few facts) then this is an excellent movie for you, and you should definitely see it on the big screen - it is spectacular. I hope they make a couple of sequels.