+1 http://www.gamesas.com/user/655675-psychomorph/
true open world kills feeling, story and immersion in what truly matters, the main quest. (which provides the ending)
The ending makes 70% of the lasting impression , so you just have to trick the user somehow in playing it till the end, and then blow his mind

Unlike some ppl who just trick the players and then sweat over deadlines.
PS: preferably those "wow" moments are well thought of and placed in progression.
For me at least, the ending of the game has equal or
less value than any other part of the game. Take R.A.G.E. for example. The ending was abrupt and not very satisfying yet all in all it was an amazing game. Now that game was more linear than open world but it makes my point about endings.
As for "wow" moments open world games can have just as many if not more than a linear game. People just have to look a bit to find them. imo it's much better to stumble across something amazing when you aren't expecting it than to know it is coming. Knowing it's coming makes it seem not quite as good, though there are times when anticipation makes it all the better.
I'd rather the producers were constantly trying to blow your mind rather than just make the ending the best part.
As for what Psychomorph said, just because the cities aren't the biggest doesnt mean anything. Sure in TES everything was on a much smaller scale than AC, but you could interact with almost everything. You could enter the buildings, you could talk to the people, you can kill whoever you like, which IIRC you couldnt do in AC even though the main point of the game was killing people, and you can go wherever you like.