The American frontier isn't the problem. The problem was the story was hugely rushed, the game was bugged (to where 100% syncs at time were impossible) and the ending was so damn stupid.
Haha, I'd forgotten about the ending. I feel for anybody who was expecting an even remotely satisfying payoff after five games of narrative build-up (well, 4 if you consider that virtually nothing happened in Revelations).
Ubisoft was hyping it up in pre-release. "Oh, yeah, we're totally going to conclude the 2012 disaster. We got you guys. *JLawOkayThumbsUp.gif*
And then it turns into... that.

AC3 also tried to reinvent a lot of shit that the Ezio trilogy had already nailed down to a science. Like, they made it so viewpoint synchronization wouldn't reveal the entire map, but you'd still have to physically wander around to fill out empty spots in it, sometimes revealing stuff that you'd 100% miss otherwise cause the game doesn't even lightly hint that its there. The fuck is the point of having the viewpoints at all then?
The worst thing about the viewpoint change is that there's an Abstergo challenge or whatever to reveal something like 80% of the map in each area, which means that, if you're aiming to 100% the game, after doing all the viewpoints you have to run around aimlessly for about 20 minutes. Top stuff there, Ubi.
The Abstergo challenges in 4: Black Flag haven't been too bad... yet. Though I'll say the 100% syncs have a few exceptions which are nearly as bad as the "do not push oh [sic] shove anyone!" 100% sync challenge that was in AC3. One of the 100% on Sequence/Chapter 10 has you stealth the
entire mission and then have to "Rope Swing Assassinate" the one target which
doesn't want to sync up with Edward's rope-swing assassinate. So it took me like... two hours... to land that thing because Edward would overshoot even if you mashed X (or whatever on keyboard) to try to initiate the assassination from the rope-swing. It's like "really, Ubisoft? You couldn't playtest this?" I mean because with the checkpoint they give you, you have to redo the entire "kill the guards checkpoints" and then try to rope-swing again. So it adds like 2-5 minutes to what should be a 2 minute checkpoint but then you have to do it via stealth instead of rushing in which adds another minutes or two to traversal.
And 10 Sequences in and you
still don't have the Rope Dart which 3: Liberation gives you in like... 4 of it's... 10? 12? 18? Sequences...

Find wasting your goddamn money funny, brehs 
Once you play one Ass Creed you've played them all. I'll catch up with Unity after the fall onslaught because it looks kinds sorta different.
I don't mind "more of the same"/same thing, I mean I want more Uncharted so formula series is fine with me...

I play Ass Creed because I like the sci-fi story (yes, shut up) and historical mish-mash with "turn your mind off" gameplay. Now and then I simply want to just auto-parkour and stab people in the kidneys, dudes.