I concur. Yes it may seem like copypasta work, but look at it this way. They found something that worked in AC2 and stuck with it. Then take into consideration that they have released a game every year thus far so developing something that innovates is a little difficult (And please if you want to talk innovation please don't compare games with 3+ year development cycles, it's kinda like comparing apples with pears).
In any case if one looks at the whole series I have not seen it go below the 80% average whatsoever so that already says that a reasonably well built engine and a strong story line, vast expanses of new territories to explore every time and a pretty awesome soundtrack makes for a good game.
They also added an interesting edge to MP. It hasn't taken off as well as they would have loved it to but still, it was something different from the usual run-and-gun side of things (or sit-and-camp for a lot of others

).
Plus for those thinking of waiting till AC3, don't get your hopes up. 1 year for development does not leave a lot of space for large innovations without huge compromises. Nevertheless maybe they have been secretly setting a team aside to develop AC3 for the past 3 years and they may shock us with a really awesome new engine without compromising in other aspects next year :3
But still, developing a game in a year that still manages an 80% average twice in a row shows that Ubisoft knows what they are doing (pain in the ass DRM aside though, but this time round they listened to the PC player base)
Just my fanboy rant for the day :3