Good chart, Steam is still king for me, I have the majority of my digital games on there, but I also have over 70 titles on GOG now. My Origin account consists of around 15-20 games, I think. I try to avoid Uplay as much as I can, it's an atrocious service.
Battle.net can burn in hell, my account got hacked and they demanded I re-purchase serials for all my games, I've not bought or played anything Blizzard ever since.
Aye, as far as things go, Steam ahs the majority of my games bought from there, with GoG in second, and Battlenet and Origin in 3rd/4th place respectively.
Uplay still needs more work and I think they should either drop their client, or take all their games off of Steam like EA has done going forward, which in turn will either force them to update their client drastically (as competition should drive them to) or they will let it die and have themselves ejected from the PC market over time. Either way, competition isn't driving them to do anything since they are making money from Steam sales, and not caring all that mucvh for the PC market (even though they keep telling us in tid bits that they do, yet I don't see it).