already on the list bad news
I agree that most of the 'extra' is entirely unnecessary. I feel like they had good intentions with Tower Defense, Mediterranean, and Templar Dens, but they're pointless at best and obnoxious at worst. For me, they didn't negatively impact the experience too much, because I put the main story as a priority, ignoring all the extra sidequests until the post-game. I think you have a good point about Brotherhood walking the line between adding compelling content and bad filler. The Hookblade is awesome, though, and I don't think most people realize how nice it is for traversal until they go back and play one of the previous games. Being able to make those long jumps and hook onto buildings is so nice.
Still, I enjoyed the story much more than Brotherhood. I liked the characters more, I liked the ending far more (one of my favorites ever, in regard to Altair and Ezio), and it was more interesting throughout. It didn't add much to the overarching narrative, but it was a good story for Ezio and Altair. Those two, to me, are Assassin's Creed, so it was nice seeing their stories brought to a conclusion. Wherever the stories goes from here is alright with me because they were given a proper ending!
--
"When I was a young man, I had liberty, but I did not see it. I had time, but I did not know it."