It remains to be seen whether Microsoft's success on PlayStation 5 as a mainstream game publisher can compensate for the decline in console sales, but so far it's pretty clear that their games have, if nothing else, found an audience on PlayStation.
This can be seen in April's list of best-selling games on PlayStation Network. Via VGC, the 10 best-selling games on PSN from April have been found, and here are the three best-selling games from Microsoft.
Microsoft is no doubt pleased with the results, but has yet to confirm an exact strategy for their first-party titles on PlayStation, but maybe that's not necessary?