Why is there no description of the game size listed in some of the new games listed?

It already does tell you the size of the game before you make a purchase. If you're making the purchase from the website, the size is listed with the description of the item. If you're making the purchase on the console, the size is listed on the pop-up
before you confirm the purchase.

You can try contacting support for a refund, but there is no guarantee that they will give you one. 1-800-4my-xbox if you're in the US/Canada or
support.xbox.com/contact-us

Hey there! It's just with Forza, right? I think we can get that behaving. Please try this:

• Delete the game again but note the file size (I beleive Forza Horizon is about 7 gigs?
  
• Head into the marketplace and download one file of about the same size- probably demos as they are free
  

• Then leave the new demo on the hard drive and download the original game again
  

Any luck that way?

[quote user="CyberAkumaZero"]A list of how large games are if you choose to install them to the HDD[/quote]Why do you need such a list? It doesn't help much as DLC gets lumped into the total size.

The game install sizes are also listed on the Xbox One game store, on the console and here on Xbox.com. The download sizes are exactly the same as the disc install sizes.

As to the install size to actual game size ratio, that one is easy to explain. The size of a game install isn't necessarily bigger because the game is 'bigger'. The size really depends on the game assets, things such as textures, high definition audio and
HD video sequences. This explains why AC4 is 7.63GB on Xbox 360, and 20.81GB on Xbox One.

It's usually listed in the game's description.