Entering crowded territory, pros and cons.

Greetings all. I'm a long time browser, and hobbiest game designer.
If I've brought up a topic already talked about, please let me kno
The question I have is this: do those attempting to create and sell games to the public go out of their way to avoid catagories (or niches) that are already being exploited well by another company? For instance, if I was to launch a pirate based board game, I'd be going into an area already crowded. I could see the "Pro" being that other game marketers have already hyped this topic, and that players might be seeking new experiances similar to the games they already have but offering a new spin on a theme. Of course I see the "Con" being that public won't purchase another game based on a topic done to death, and one that they already own. I suppose its like trying to launch anything new, is its catagory market saturated or not.