On one hand, the fans make the game.
The team that made Devil May Cry 2 made Devil May Cry 3.
Their giant improvement is due to the fact that they listened for feedback from hardcore fans who had played DMC 1 so much.
In fact, one of my favorite directors (Joss Whedon) subscribes to the idea that being a director is never about making something that fans like. It's about making something that fans love.
On the other hand, fans can ruin something too.
For example, inFamous was a pretty cool game. It had a bald protagonist only because their developer Sucker Punch didn't want to use up any processing power rendering his hair.
They released some teasers for the sequel and the protagonist had grown hair in the four weeks after the first game ended, along with changing his clothes.
Fans didn't like that, and Sucker Punch changed his hair right back.
A very pointless change, in my opinion.
The developers should make something they're going to be proud of in the same way artists should create something they're proud of that they would want to play.
It can go either way after that.