I had a thought and would love to hear your opinions about this, maybe there is a way for us to make it a reality :)

Let me start with an example of what happened to me a few years ago: I bought L.A Noire on Steam, but after I downloaded it, I saw that the game is not working so well on my PC.

After a few months I bought PS3 and saw L.A Noire on the PS Store. I was wondering...why do I need to buy this game all over again (full price) if I want to play it on my console?

What if GOG will ever be shut down (god forbid!), would I have to buy Escaping Goat on Steam again?

I mean, I fully understand that porting to other platforms is not a push of a button, but it's not a full production either. So Team Bondi already got my money and gave me the rights to play this game, why are they expecting me to pay for it again, with full price, just to have it on my PS3?

I would be OK if they already knew that I bought the game and gave me a special low-cost price for it. The same should go for games/apps on the mobile stores.

As long as it's a digital download, don't charge me full price for the game. I already bought it, I just want it on a different console. And I'm talking about games that are the same on each console of course, mobile games are not the same as the consoles and I wouldn't expect to buy $5 Batman game and also get it on my console :p

I know that it takes a lot to make all of these companies work together, and I know that if they can charge more, they will and that they don't have any interest giving us cheaper games, but isn't anything we can do to force them? I don't know...go on a strike or something? Make a day that nobody will buy games?

What do you think?

Unless something like an old unique serial number was provided with every purchase, something like this would need some kind of DRM. Not to mention the IP holders and publishers for different platforms could be different or fall under different agreements. You wouldn't have to. With backup offline installers, you'd never need to log in GOG again to ever install your games. If GOG closed down today, I'd lose zero games. ;) The wonders of DRM-free!

Storefronts of any kind are there to make money through trading, they are not here to provide services to you. It’s that simple. If gog allowed you to download anything you brought on steam, gog would go out of business very quickly (and vice versa the other way round).
Therefore this is never going to happen.

As already stated, the storefronts make their money from a cut of the sale of the game, so if they aren't selling the game they make no money.

The only way this could work would be if the games were purchased directly from the developer and the developer made the different versions of the game available from their storefront. That could work for large companies that have invested in storefronts already. But this isn't realistic for most small to mid size companies who don't own storefronts.

This also ignores how fragmented the publishing of games is. Games are published by different companies on different platforms and in different regions and all those people want their cut of the sale of the game.

The entire sales model of digital goods would need to change for this to work on any reasonable scale.

As long as corporate greed rules, and most importantly, we have open marked (i.e. not monopoly), we will never see a buyers/consumers-marked like that. Just look at the current streaming situation; more and more wants to have their own IPs, solution and storefront.

And who's ultimately paying for it? Yep, we are, but it's our choice to choose between platforms and stores!

Problem is; let's say I buy a game at GOG, and then request for whatever reason a copy, or access to a copy at Steam for free - who's going to pay for it if not you? Who's going to pay for manual service support, server use/space, server maintenance, and electricity among other things?

Another thing; monopoly / closed marked would effectively kill competition and, subsequently, kill many creative works. ...unless we're going for a money-less civilization like on Star Trek, but by then everything in our civilization has changed anyway.

TL:DR - Without this open marked / competition you wouldn't have access to myriads of games you want access to on different platforms in the first place. ;)