CDPR and Bethesda as far as hours go. As for which publisher's games I've finished from start to end the most, probably Capcom. A lot of their games are fairly short with a lot of replay value.
So, with them having Fallout Scrolls and Forza under the same roof, I don't think anyone else compares. Not to mention I got a few hundred hours on Doom Eternal because I had a phase where I was playing Master Levels and higher difficulties. Not to mention Quake replays and modded levels. Also have a hundo+ each in Dishonored 1 & 2 and Prey. Rockstar has to be close, but it's untrackable because my GTA 3 trilogy was all done on PS2. But they're close, espcially when you factor in the old Max Payne duo.
But if we pretend MS isn't a demonic gaming homunculus, it would a tight race between Bethesda, GSC, Forza Franchise and being Miyazaki's pay pig.