What does a modern hobby game store do? What role does it play in serving its customer base? You have two major factors, what's desirable and what's obtainable. These are elements of demand and supply, but not quite the same.
Desirable. What generates desire is often outside our control. Most of what is desirable is locked down in existing markets. For example, we have 30 companies that make up 80% of our sales, despite having several hundred on hand. What Magic players want is not something we control, generally. In fact, the desire for this is product is created externally from us. The publisher and its designated agents create the demand. As a store, we can run events to foster this excitement, make social media posts, and generally get excited, but for the most part the desire for this product is external from us. When you think you'll open an "X" store and sell particular products, you are hoping your small bit of enthusiasm will translate to strong desire. You'll sell what they let you sell.
You can also create desire through experiential retail. Events are the obvious Useful Value Proposition. Demo tables with active selling will take well vetted product choices and exponentially increase sales. More demo tables, more sales. Without experiential retail, you will not have a value proposition and will probably fail. With just events and no active selling, you'll be working a passive retail model that will be determined entirely by foot traffic and population base. Creating desire for product is often the difference between break even and profitability. The bar is high.
Obtainable. Obtainable product is stuff you can get, at a margin or price you can deal with, in reliable quantities to meet your needs. You may overcome some of this with enough capital or size. There is no margin too small, only a price you mark up to that people are unwilling to pay. There is a huge swath of consumer goods, that you would think we should be selling, that we're locked away from because of lack of distribution, direct sales, or our volume is simply too small. We're are often second choice for a lot of products, so the more niche the product, the more likely the alpha customers will have it by the time you get it. If the product is entirely niche, the market may not exist at all. I have this problem with many Kickstarter games, especially role playing games.
Mainstream vs. Niche. This means our real role in the marketplace is to have the most mainstream products for the most mainstream customers. Niche products serving niche customers is something we engage in, but it's a sideline to carrying the top products for the average customer. As store owners, we like to be niche. We like to delight customers. We do end up spending a lot of time and money differentiating ourselves by seeking out niche product. Just today I had a niche RPG arrive (which everyone loves, but nobody will buy) and a long awaited, classic board game (which everyone loves, but nobody will buy). These make me happy. They send a message about the kind of store we are. They will not pay the rent, and thankfully both publishers took my money over a year ago.
If you are a customer looking in, you probably only see the things that interest you, the niche product probably. As a store owner, we are much better off putting our thumb on the scale, so to speak, than seeking out new product to weigh. Tweaking my Magic prize support or drumming up a Yugioh event is likely more profitable than my next five backed Kickstarter projects. It is our enthusiasm for cool stuff that keeps us driven to find new, delightful product for our customers.
The 45 degree slope. Finally, imagine a chart. You have desirability on the vertical access and attainability on the horizontal. A line runs at 45 degrees, cutting this graph in half. Everything on this line or slightly adjacent, you can sell. Everything else is either not desirable to your customer or unobtainable. Each product could be charted on this graph. At least, it could be if we knew what they are. Each desire is likewise a mystery. We don't know where customers spend their overall entertainment dollars. The stuff that aligns along this narrow corridor is the stuff my store sells. Sometimes I grasp for items far out in the distance of attainability. Sometimes things are game store exclusive and we see demand that hints at a larger universe we're barely part of. Sometimes we can channel desire to what we already have, but far less so than we would like.
Surviving in this trade is acknowledging your line and working to bend desire and product towards it. It's also realizing when you're being played, when you're being asked to create desire for the unobtainable, or promise the unobtainable in ways that won't satisfy desire. Pull desire on top towards the line, attain product from the bottom towards the line. This is maddeningly difficult. This is the work part of the job.