Weren't all the "side quests" just the exact same "Save Citizen" event? Even the primary assassination missions have you repeat the exact same chores over and over again... eavesdrop on conversation, pickpocket target, stalk and beat up a preacher, again, and again, and again... The game hardly ever makes use of stealth, instead pushing you into open combat almost every single time! This especially gets annoying towards the end, where you usually have to fight entire legions in open combat, and unless you want to get used to the loading screen, you have to master counters and combos. Oh, and don't get me started on... them. You know who I'm talking about; those crazy troublemakers that shove you around for no reason, usually on (and causing you to fail) missions. I could handle the beggars and the minstrels, but I will never forgive whoever designed these painfully frustrating obstacles!
But, the one good thing about Assassin's Creed is that it delivered a powerful sequel. ACII was really the game ACI was trying to be, but it would take the developers the experience to learn from their mistakes before building their dream game.