Since game design is a business, I decided to see what's really selling well for the PS4.

I did this search a week ago, and at the time, out of the top 20 bestsellers on Amazon 10 had not even been released yet. By now some have been released. But others still have not. And yet others are still months away from hitting the market.

How great would it be if you had a video game development company and made all these sales before the game even came out?

You'll notice that America's love for football clearly translates into video games because both Madden 15 editions (standard and the ultimate) grace the list.

So what is it about these games that people can't wait to purchase? Why do people buy games so far in advance? Why do people pay for these games months before they can even play them (weeks I can understand)?

So here are the 10 games that were yet-to-be-released for the PS4 that were sitting pretty in the top 20 of Amazon's bestseller's list last week.

Madden 15: Standard Edition

Release date: August 26, 2014

Price: $ 59.99

Destiny

Release date: September 9, 2014

Price: $59.96

Madden 15: Ultimate Edition

Release Date: August 26, 2014

Price: $69.96

Call of Duty: Advanced Warfare

Release date: November 3, 2014

Price: $59.96

Assassin’s Creed: Unity

Release date: October 28, 2014

Price: $59.96

FIFA 15: Ultimate Team Edition

Release date: September 23, 2014

Price: $ 69.96

Call of Duty: Advanced Warfare – Atlas pro Edition

Release date: November 3, 2014

Price: $119.99

NHL 15: Standard Edition

Release date: September 9, 2014

Price: $59.96

Middle Earth: Shadow of Mordor

Release date: September 30, 2014

Price: $59.96

NBA 2K15

Release date: October 7, 2014

Price: $59.99