That's true the real comparison is between PS Now and Game pass. Should be able to tell which subscription service has had more growth then.
If you want to compare PS Now to something, compare it to GPU even ignoring the $1 Gold to GPU upgrades. But we can't because MS doesn't release the numbers.
To compare Now to GP also isn't fair because in Now you don't get $1 Plus to Now upgrades, 3 free months of PS Now in many places. And PS Now, like GPU/xCloud is only available in a few countries, while Plus and base Gamepass is available worldwide.
If it's real that they will merge Plus and Now into Spartacus and that they'll add an additional tier that it would be like base gamepass (available worldwide, would have the downloadable content of PS Now), then Spartacus will be comparable to Gamepass.
The fair comparision now would be Gold+GP vs Plus+Now. But again, MS doesn't provide the Gold numbers. I assume because most of them migrated to GPU using the $1 upgrade. So as of now we can't get proper comparisions. Same goes with revenue, Sony provides the revenue of the SIE 'network services' (Plus+Now) but MS doesn't provide any revenue from Gold, GP or GPU.
What I’m trying to say is that gamepass reaching 200 million subscribers is a pie in the sky.
We also have to consider the size of the people who can be interested on gamepass, which would be a portiion of their fans. Let's say XBO sold 50-60M, being generous 60M. Let's assume they achieve the unrealistic assumption that all 100% XBO owners get GP. Let's assume they get some extra fans more from PC, mobile users that already weren't on XBO, and also coming from the teams they bought (Bethesda, ABK, etc) that already weren't in. I think that even bein unrealistically optimistic, they won't reach 100M. I think that being realistic, they have potential to peak at 50-60M with GP, and it would happen before the release of the next generation.
Meanwhile if it's true that Spartacus would be released this Spring and that it woud feature a base gamepass like tier available worldwide that would include the downloadable content of PSNow, and tthat the service would merge Plus, Now and would add extra content on top. I think that this same fiscal year they already will have these 50-60M plus unlike GP, this Spartacus service would be profitable because they won't be putting all their AAA games plus some 3rd party ones day one there.
And I think this Spartacus service would grow beyond these 50-60M because PS has 111MAU as of now and they are also supposed to open the streaming to mobile/tablets/smartvs soon. And even considering this, it will be continue being a secondary revenue source for Sony, whose main revenue source will be games and specially digital add-ons (mtx/dlc/season passes) being sold for their console.