RE: Epic Games (creators of Fortnite) and their 'Epic Games Store'
Yeah I agree with you. Some games will be available only on steam whilst some will be available only on the Epic Games Store, and this means that buyers will invest in both of them. Though as for the 88% revenue for the developers, I think it's great. Steam will try to match with this, so far they have already put something in place: https://www.engadget.com/2018/12/01/steam-gives-successful-developers-a-larger-cut-of-game-revenue/
But Epic Games was the first to make that change and that means a lot. I feel like most developers (who mainly use UE4) will now switch to Epic Games.
The whole thing was a good move on Epic's behalf and Steam now isn't the only PC gaming giant (at least not until Epic Games Store gets it's footing.) I hope it doesn't break out into war, and they can exist in peace like Steam and Humble and GOG.
As for me most of my games are on Steam, though I didn't have Subnautica on Steam so I picked that up and have already started my Epic Games library.
I didn't have Subnautica either, a nice game to have as the first game of my Epic Games library (not taking Fortnite into account).
Steam's new revenue share was actually announced a few days prior to Epic Games announcing their store. I doubt it was a coincidence, Valve must have known what was going to happen, they just didn't know how low Epic Games' commission would be. Epic Games still isn't the best one in terms of commission though, itch.io has for a long time allowed developers to set itch.io's commission percentage and Discord just released a statement about lowering their commission to 10%.
I believe too that most developers using Unreal Engine will migrate to the Epic Games Store. They are the ones that get the most advantages from this. I also believe that a big part of AAA games that don't already have their own platform will switch to Epic Games. It's all about money for publishers of those games after all. This proved to work in the past with platforms like Origin, Uplay and Battle.net, I have no doubt it will work again with the Epic Games Store.