Probably Bethesda for my personal taste. Kinda hyped for Starfield, I thought Doom Eternal was great, Fallout 4 was fine for me, never tried Fallout 76, Elder Scrolls feels like an eternity away.
At their peak Blizzard alone was better than Bethesda though. When WoW first launched, Diablo 2 + Expansion pack being released, Warcraft 3, Starcraft Broodwar etc. Maybe Blizzard was the best game dev of the world at that time.
Those days are long gone though. Diablo 4 looks decent and I am kinda hyped for it. If Blizzard has a game that slaps then it god damn slaps, but anyone that had any talent or passion at Blizzard left in the last 3-4 years.
So it is a bit of a dilemma. Lets say Diablo 4 is a 10/10 hack n slay, arpg, whatever you want to call it and it comes out and feels like a perfect modern interpretation of a long lasting franchise then it could be that 1 game alone is enough to be better than the entire catalogue of Bethesda, but it has to be extremely good.
Current form -> Bethesda
Peak potential -> Blizzard