Expectations, similarly referred to as hype, is an extremely important aspect of selling a product.

Controlling expectations might seem imposible, and ultimately it is to a degree, but how it is handled can significantly determine the sales performance of a product.

With regard to products in the gaming industry, the control of expectations involves three important factors. 

The actual expecations and the substance of the product itself and the reception of that product.

Keep in mind when I say "seller" I mean developer, producer, company, whoever is responsible for the game's marketting hence control of the expections, etc...

In terms of the amount of control a seller has over each of these factors: the substance, which the seller has direct control over, the expectations, which the seller partially controls through marketting, and reception, which "ideally" the seller cannot control.

By maintaining the balance between expectations and the substance that can actually be provided reception can be controlled to the degree. Although, exceeding expectations is generally a positive, there is a cap, a point at which the disparity even when exceeding expectations becomes pointless.

However, reception is only 1/2 of the part of the issue. It increases a products sale duration and consitency, however low expectations can decrease the sales potential of a product. So a seller must endeavor to raise expectations, i.e make people excited about there product, aka hyped.

So a seller must raise expectations of a product in other to increase its sales potential, but have it meet or exceed the substance provided to bolster the reception and make it have legs. Raising substance to a high enough level of expectations is difficult enough in some circumstances, so its not hard how to see how things can get "overhyped".

But you might be saying to yourself, "But Dr. Killinger, I am in control of my own expectations!" 

Watch this:

https://www.youtube.com/watch?v=druOAHVKHCQ

https://www.youtube.com/watch?v=JQZFTbPh4jM

https://www.youtube.com/watch?v=cSPRKL0xzVg

and this if you have some time:

https://www.youtube.com/watch?v=qiKMmrG1ZKU

Now lets get to the meat of this OP, The examples :D as I aim to link alot of phonomena in the industry to this control of expectations.

Wii U: Average -> low expectations + Avg -> high substance = increasing reception + poor sales

PS4: Average -> High expectations + substance that meets expectations = great reception + great sales

X1: Bad expecations -> Average expectations + Bad -> Avg substance = avg reception + increasing sales

Titanfall: Extremely High expectations + Average substance = Lukewarm reception + high sales

Destiny: Even higher expectations + Average substance = Bad reception + High(initial sales)*

Smash: High expectations + (actual subtance unknown) = (reception unknown) + (sales unknown)

intial cause we have no idea if they could fall off a cliff.

The phenomena known as overhyping is merely a mismanagment of expectations. In the case of Destiny, while I don't have enough information, to talk about it sales, its critical reception can be greatly attributed to they way it was marketed and the way Activision set up expecations for it. For example, the most common complaint I read about the game is its monotony and its apparent dearth of scale and content. This is probably due to the fact that Destiny was marketed as a fresh, innovative experinence taking place in a huge dynamic world. Sure they wanted to set expectations high to make up for its substaintial budget, but the way the game itself was designed, in the style of an mmo with expanding content base, that would require time to become fully fleshed, it was clear that this was a set up for disaster.

When you promise so much, its little wonder its very easy to underdeliver.

Waiting for the tl;dr version.

I always put those at the end of my OPs.