Or you could just leave the in the cases and only take what you expect to need out or the warehouse at the beginning of the day. Since the cases leave with the customer you'd still need to hit up the warehouse anyway if you ran out, so all you've achieved (aside from making sure sealed games aren't easy to steal as I've said) is a make work project. Of course, that would depend on your store. At mine the "warehouse" are small rooms that double as the manager's office, so I doubt there's much more stock than what out.
Doesn't work because those 300 games could all be different unique games
you have no idea what you need because you don't know which of the 300 games the customer will randomly walk in and buy
your scenario is assuming all 300 games are copies of call of duty (an example)
And the shelves have unique cases (or at least papers in the cases) to identify the game you're buying. So either way you have the same space taken up by game boxes for a mix of specific games (10 COD, 10 Assassin's creed, 10 Halo, etc) be it empty cases or sealed ones. Of course, I've never seen a gamestop (or any other store for that matter) that didn't just leave the inventory on the shelves at the end of the day. ---