No, they double it. Once for the reseller, again for the person who buys it from them. I am saying demand, you are saying sales. The reseller and the their eventual buyer both want the item from the retailer, which is twice the demand (but for different reasons). The reseller defers the sale.
How many people wanted to preorder yesterday, failed to and bought one on eBay? Those people wanted it for their own use (their contribution to demand) but the resellers wanted it to resell (their demand contribution).
Your definition of demand is myopic and short-sighted. A reseller can certainly contribute to the hype and INITIAL interest in a product. However, without a buyer, a reseller is not going to sit on their product and will return it to vendors. The key here is that a reseller has no interest in actually keeping the product for their own use, which is what will factor into the ultimate demand for a product. Demand is determined by the consumers that permanently remove it from the market, reducing the total supply in retail channels.
The definition of demand is "the quantity of a commodity or a service that people are willing or able to buy at a certain price." It is clear that the demand for the product at MSRP is greater when resellers are factored into the equation, there are simply more people involved. However, the very inclusion of a reseller will increase the market price for a product. Increasing the price decreases the demand, a basic tenet of the law of supply and demand. So long as the total quantity of a commodity or service (SNES Classic) are being purchased by consumers, at either MSRP or after-market value, the demand has not changed.
If left to their own devices, resellers could always try to drive the market price up...beyond the point which (some) consumers are willing to pay. In this case, the economic demand for the product would actually decrease, since the total quantity of a commodity/service that people are willing/able to buy at this price would become lower. This is unlikely to happen, since the reseller price point will naturally tend to gravitate toward the price which people are willing to pay. So long as retailer inventory is moving to buyers, the demand for the product remains constant (and above the level of supply).
This all goes back to my initial point - a reseller has absolutely no bearing on the long-term demand for a product, since they do not intend to keep the product. Collectors, on the other hand, DO factor into the demand since their purchase effectively removes the product from available supply. Of course, a collector may eventually sell their product (there is a grey area between what we define as a short-term collector and a reseller), but this eventual sale will generally occur at the price point defined by the current market for the product (the demand).