I used to like Gander back in the day. There's one near me and it doesn't even register on my radar as a place to visit these days. I don't think their selection is as good as the other big stores in the area, and their prices are astronomical by comparison. These days if I can't find it at a local shop, Cabela's, Bass Pro, or Sportsman's Warehouse, I just order it online. I'm really not surprised to see Gander Mountain go bankrupt.
EDITED TO ADD:
More and more it seems like all brick and mortar stores are being hurt in favor of online shopping. This isn't always possible for gun stuff, but it's still surprisingly handy, even for gun stuff. When I built my SBR AR-15 I tried to buy stuff locally, but just couldn't find any of the parts I was looking for. I bought my stripped lower, my optic, and a barrel nut locally. The trigger, barrel, upper, stock, buffer tube, buffer, spring, lower parts kit, upper parts kit, and iron sights were all purchased online. It's a bit of a conundrum really: if I can't find it locally I buy it online, which hurts the local stores, and makes it harder to find the stuff locally in the future. But, it is what it is. Times are changing. Still, the local stores would do well to have better customer service. I get some of their other issues, but bad customer service is inexcusable, and Gander suffered from this problem for a while, too.