Stop me if you've heard this one before....
A guy walks into a bar and orders a beer. The bartender lifts his eyebrows and says, "instead of ordering that yucky national brand, you should try this local brew."
You think for a second, shrug, and say, "what's so special about it?"
The bartender harumphs and says "It's local, and it's the same price."
At this point, if you care about trying new things, or want to support something local, then you can base your decision about whether or not to try the local beer on one of those criteria. The only difference the bartender used to differentiate was that one was local.
I chose beer, but this is a "conversation" that occurs in every industry. It happens in the halls between product managers, marketing people, sales people, and on and on, up and down the line.
This decision making occurs with buyers and consumers often at a subconscious level, but sometimes they will verbalize it as "why should I try your widget instead of this one?" Or the classic "I already use this widget, why should I change?" (you'd better have a GREAT answer ready for that question, BTW.)
This boils down to differentiation.
Differentiation can come from anything, really. But the one important factor you have to remember with differentiation, is that it occurs in the mind of your target audience.
Differentiation is defined by your target audience. It's only differentiation if they find it meaningful or relevant. Not you.
For example, you've designed a board game where you place workers on spots to activate actions or generate resources. You decide to make it about zombies. Does that mean it is differentiated? Maybe - maybe not. Maybe you should ask some gamers who like zombie games for their opinions. Or, ask gamers who like worker-placement games. My vote is to ask them both.
When you are designing a game (AKA "developing your product") hopefully one of the earliest questions you are concerned with, and asking yourself is, "is my game different?" And that's a hard question to answer.
Hopefully you'll ask that question early in the design process, because the traditional product development theory is that the sooner you make design/development changes, the easier and less expensive they are to make.
So, think about differentiating your game. Think about it as early as possible, and keep thinking about it throughout your design and development process.
There are thousands of game submissions passing through game publishers and being Kickstarted... and you'll stand a greater chance of getting their attention - and the attention of gamers - if your game is differentiated.
Have fun designing your game - keep differentation part of the process - and good luck!