A few reasons why this sucked for you would be great.
Main reason is story, I just don't like it. US, and it's cities, going through forests, the time, the gameplay, (why on earth I have to manually select the hidden blades is beyond me) playing with double characters, meaningless ending other than the fact this was the last AC, and a lot more. I just didn't find any 'thrill' in this, too much open field combats.
Good things, well, graphics, the background audio, and a little tougher and lengthier than previous ones.
Anyway, what I think or say doesn't matter, you liked it, that does.