Assassin's creed series is purely about climbing and diving off historical buildings, the Erich von Däniken novel copy pasted into the game should be ignored as much as possible. Ubisoft stories are only decent when they are relatively low-key and don't try to be dark and epic (compare Sands of Time with Warrior Within) and plot twists are always terrible (even Beyond good & evil is guilty of this).
AC1 avoided the nonsense until the very end and while the game was (too) repetitive, combat at least required some effort. AC2 combat is soul numbing, at least in Brotherhood you can chain kill or summon your bros to do the dirty work. Also, fist fighting the goddamn Pope.