Xbox is aiming for one first party title per quarter minimum and this was before the ABK acquisition. If 4 is the minimum we can expect some years with 6, 7, or 8 titles. Sony currently has 22 studios. I counted 17 that are actually making games, the other 5 are support studios. Out of the 17 studios that are actually leading projects, we have London Studio who hasnt made a significant first party game for Sony since SingStar in the late 2000’s, Media Molecule who seems to be making Dreams indefinitely, Sony San Diego who makes MLB the Show and releases games straight into Game Pass, Recently acquired Savage Game Studios who has a head count of a dozen people and makes mobile games,. So out of 17 who are leading projects, there are 13 who are considered the “core” sony studios working on regular releases in the single player or GAAS space.
Sony announced they are making 25 games including mobile and live service. The count for Xbox atm is 76 and growing, including ports of previous PS exclusives.
Post ABK Microsoft will have 33 studios. They have 23 studios now, 3 of those include Mojang who are multiplat, Alphadog and Roundhouse who arent making anything right now and are supporting Bethesda.
So if you want to use my logic, its 13 studios vs 20 for MS who are busy making regular first party/non multiplat games. And that is BEFORE ABK, which increases the studio count significantly. The current project count for MS can be found below.