Exactly what opening says, which of this generation's games broke expectations in sales?

You can break it into 2 tiers if you like!  Ex: Game "A" was higher than expectated but Game "Y" Was incredibly unexpected in sales!!!

Here are mine off the top of my head...

⇒Did Better than I thought

⇒Completly Unexpected!!!

Also would of put Persona 4 Golden but i didn't kno about it at the time so i have no opinion on it

Shouldn't this be in sales discussion?

Knack only did so well because it was bundled in Japan

Did better than I thought:
Killzone: Shadow Fall
Knack
Wii Party U
New Super Luigi U
Dead Rising 3
Ryse: Son of Rome

Did worse than I thought:
The Wonderful 101
Pikmin 3
Rayman Legends
Splintercell: Blacklist
Super Mario 3D World

Might add more later, if I remember anything.

Edit:

Did worse:

Sonic Lost World

Even without Japan it has done 600k and counting on a small install base. I doubt many people expected that.

2 things 

1. That thread i just added LM2 to the poll, that was it. Let it goooooooooooo

2. My prediction was around 4-5mil lifetime, but yours was a measly 1.2mil which its already 3x as much! :P (probably end up around 5.5mil lifetime)

The install base is kinda large, actually, at least compared to the other next-gen consoles. 

If we are talking about the community as a whole, I'd also add 3D World, because everyone "knew" Knack was gonna outsell it, and soon coming Mario Kart 8 because there are people who don't think it will boost the sales of the Wii U. 

As for me personally, nothing is really selling better than I expected to be honest. Titanfall has sold way less than I expected. Other than that top sales go to the usual suspects, COD and Battlefield. No surprises.

When It comes to X1 and PS4 I can't really say any game is doing better than I thought since people are desperate for games so most will pretty much buy anything that is available. (One of the reason's I've gotten into Indie games due to the lack of a large library of games at the moment).

In comparison to the other systems, yes. In comparison to Knack sales, not really.