Stacking the games vertically has its problems. I've put up with them for the whole span of my collecting career, as removing a game lower down can cause the ones above (which were held up by the very game I just removed) to fall. As can be seen in the photos, though, I'd like to think that I've fixed this issue with planks of wood cut to size which act as dividers of sorts.
I had a ball of a time measuring up and cutting those pieces of wood to size - essentially creating mini shelves within shelves. I even cleared an old woodworking bench in my garage (once owned by my Grandfather) to carry out the deed - which made it quite a simple and fun exercise. I wish I used that when I attempted (and failed) to create a console shelf years ago. I probably would have finished the damn thing.
Talking about that shelf, I actually used the wood from that failed venture for these dividers. I got a real kick out of actually using that wood for my little retro gaming world - even if it wasn't its original intended purpose. Next on the list will be to varnish it up to somewhat match the finish of the cabinet. At least, I'll attempt to anyway. I've never done anything like that before - but hey, I'm sure Google will point me in the right direction. That and the 1960's book on woodworking I bought from an op-shop recently, anyway.