Mainly because it really has nothing much at all to do with the actual story, and ends when he's banished to the forest and his followers go with him. The story was good, I guess, but not the story of Robin Hood.
I also didn't particularly like it because although there's plenty of battles, Robin does very little archery... there's none of the cool traps laid in the forest (because none of it takes place there) and other than the classic arrow piercing the reward notice to the tree, there's no cool archery either.
Oddly enough, although there is a Sheriff of Nottingham character, he's basically a walk-on with one or two lines and a wimp rather than the evil bugger from the story. Instead, the villain is some French dude. There's no stealing from the rich to give to the poor and battling it out with the sheriff.
Oh, yeah... it's not the least bit historically accurate in that King Richard gets killed in the Holy Land right at the beginning which also kills a lot of the point to the actual Robin Hood story. Robin Hood isn't Robin of Locksley either but some nobody that pretends to be him.
Like I said, a good story, but aside from the character names of Robin Hood, Marian and Friar Tuck (can't even remember if Little John was a character at all) I have no idea how they got away with calling this a Robin Hood movie because it just plain isn't.
Funny that you posted this because I just found out about the BBC tv Robin Hood series from a few years back and have been watching all the episodes on YouTube. This is my favorite Robin Hood film EVER. Keith Allen that plays the Sheriff is AWESOME and the guy that plays Robin's servant sidekick "Much" is hilarious. The actor that plays Robin Hood (Jonas Armstrong) is a skinny bitty little guy, but considering that archers were the little guys and with all the sneaking about and breaking into and out of places he has to do, I really feel like a skinny little dude makes for a better Robin Hood. Richard Armitage plays Sir Guy Gisborne (the Sheriff's sidekick/deputy/fix-it man and personal assassin), who is the one that has the hots for Marian rather than the traditional story line of that being the sheriff, but I think it's an improvement because it makes the sheriff much more easily despised (although he's hilarious in his evil). One thing that's really cool about is that they throw in a lot of modernisms both in references to general things people would know, common slang, and even better it sneakily parallels current political, economic and particularly foreign affairs and you notice. Some of the references to general stuff is for example, in one episode a certain character believes he shot the sheriff with an arrow and while dying on the ground proudly exclaims "I shot the sheriff!", and the sheriff saunters up and taunts "Noooo, actually you shot the deputy") - a reference to the reggae song "I Shot the Sheriff". There's lots of fun little things like that in the series. It's a great mix of comedy, action and some real boo-hoo drama. The cinematography is really surprisingly good (something I'd expect from a big screen blockbuster movie), and the music is really good.
If you haven't seen it and are interested, here's the page on YouTube that has almost all the episodes (all of seasons one and two and the first two episodes from season three)....
http://www.youtube.com/user/Vampires22#p/u/90/sJpN47BG5UUHere's the first two episodes for a taste...
BBC ROBIN HOOD - Season 1 - Episode 1 - Part 1
http://www.youtube.com/watch?v=qrjCfuJCwUUBBC ROBIN HOOD - Season 1 - Episode 1 - Part 2
http://www.youtube.com/watch?v=fogM2xwRylUBBC ROBIN HOOD - Season 1 - Episode 1 - Part 3
http://www.youtube.com/watch?v=g3c2mCymz4MBBC ROBIN HOOD - Season 1 - Episode 1 - Part 4
http://www.youtube.com/watch?v=X-qmRnk-vpkBBC ROBIN HOOD - Season 1 - Episode 1 - Part 5
http://www.youtube.com/watch?v=pCRI-cjeZOUBBC ROBIN HOOD - Season 1 - Episode 2 - Part 1
http://www.youtube.com/watch?v=pqiHeGmrN-gBBC ROBIN HOOD - Season 1 - Episode 2 - Part 2
http://www.youtube.com/watch?v=LhdLZadFfM0BBC ROBIN HOOD - Season 1 - Episode 2 - Part 3
http://www.youtube.com/watch?v=IPfJBEQrK4kBBC ROBIN HOOD - Season 1 - Episode 2 - Part 4
http://www.youtube.com/watch?v=FCEMAZxF-hABBC ROBIN HOOD - Season 1 - Episode 2 - Part 5
http://www.youtube.com/watch?v=j_ZtleAdMI0