Not every game needs to be a genre bending, mainstream AAA hit that ignores the pleas of fans in order to push more copies just like not every game needs to be a fan service filled, niche title that won't expand the fan base.
Should developers listen to fans? Well the answer is yes, they should always listen to them Should they always do what the fans want? Probably not since you can bet that they'll often get lots of conflicting demands.
At the same time, however, how many franchises have been killed by developers or publishers ignoring fans. The new Call of Juarez is clearly saying something along the lines of "Hey old school CoJ fans, if you don't like CoD then SCREW YOU!" and even if people still like the old style of CoJ and CoD the developers basically still said "Well now you're stuck with a modern conflict based FPS so deal". Well, maybe there are less fans of westerns out there than there are of dark and gritty modern war shooters but why forsake your die hard fans? What, for money?
The problem is that all to often too many game publishers are only focused on the bottom line and they want a game that will sell to EVERYONE and they don't want the chump change of a niche market. Flight sims, RTSs, mech sims, space fighter sims, those all have strong fan bases and many would love a new game in their favorite franchise but many also know that they'd likely get a watered down piece of garbage that say "F**k of fans, we're going mainstream and you can't stop us. Convert or die."
So, yeah, listen to fans for niche market games and for big, mass market games don't even bother those people are usually so concerned with brand names and multiplayer that they'll buy about anything you spoon feed them.