How are you doing Market Analysis on Competing games?

Hey everyone,

How are you analyzing games that are similar to yours to determine what players like and don't like (besides playtesting)? What data are you gathering that tells you feature X or feature Y is what players like and why they like it? How do you determine the demand for your game?

For instance, given game A with 2,000 reviews and 2m in sales, how can you determine how much your own game is likely to sell when factoring in your own spin / design?