I actually know exactly what you're talking about, in every sense of the word, O.P.
When I was young--back in EB Games was still a thing here in the U.S.--I remember walking into those stores and being floored. Hidden treasures were everywhere. Games I'd never even heard of. I found Suikoden II on the shelf, brand new, after having just beaten Suikoden. I had no idea there was a sequel, and my brother and I immediately begged our mom right then and there for the game. Those were the days.
Even during the PS3/Xbox 360 generation, walking into those stores was still a treat. You could find games dating back ten years, sometimes even more, just sitting on their shelves. Sometimes they were scalping prices, but other times there were steals. It was a fun way to just go through all their games and see what I could find.
But something has clearly changed. When GameStop announced that they would no longer be selling or taking PS2/Xbox games and older, the magic died. It's not longer like looking through a fun candy store in wonder. It's like going into a "candy experience" where only the top selling (or so says the management and publishers) candy is for sale. It's so depressing. I look at the PS4 shelves and I barely see anything. The PS3 games are just the bottom of the barrel stuff, or games so popular of course I have a copy of it. That sense of excitement is long gone, and I find I get more joy just browsing the PS4 store now than I do actually going into GameStop.
Amazon is great too.