Hmm tricky choice. True Crime/Sleeping dogs was excellent though and superior to GTA in every way, for me. So I would rather see that over anything else.
Though I am terrible at the game and get stressed and “stutter” while playing I love watching a good Starcraft Tournament, so I would have some love put into Starcraft for that reason alone.
Though as @Mort said Starcraft Ghost v2.0 would be cool.
Warcraft, Starcraft, Gun, Prototype.
Make Warcraft and Starcraft have as much transmedia expansion as something like Warhammer.
I wouldn’t expect the biggest budget in the world, but if MS can allow something new for one of the Sierra Quest games then that’d be perfect for me.
I would love to see what the coalition could do with Blackthorne.
Singularity, True Crime and Blur are my top picks. If they got the Marvel licence back I would add Marvel Ultimate Alliance.
I would be fine with any of them that end up as fun games, but I will say that King’s Quest holds a special place for me as one of the first games that I played on a home computer with a giant stack of floppy disks to insert when walking off the screen into a new area of the game 
I prefer them to form a studio (with current and or new employees) that focused on Sierra legacy IPs. Just 100 devs at max seems enough for a combination of new games & remasters as long as ultra realistic graphic or AAA checklists isn’t one of their priorities.