Here's Ryan Clark (Crypt of the NecroDancer) writing about what makes a game commercially viable:

http://www.gamasutra.com/blogs/RyanClark/20150917/253842/Wha...

Here's Jan Willem Nijman of Vlambeer discussing a large number of small improvements that make games feel good:

https://www.youtube.com/watch?v=AJdEqssNZ-U

Here's Rami Ismail, also of Vlambeer, explaining how making a game a week helps you develop an intuition for some parts of game making:

http://ramiismail.com/2014/02/game-a-week/

Here's a talk by Sid Meier (Civilization) about Interesting Decisions:

http://www.gdcvault.com/play/1015756/Interesting