i wonder how long they will last? jk

maybe its a game that will challenge sony's baseball series

Perhaps they acquired them for their current titles and dare I suggest given the teams history that PGR5 may need a developer. Whatever the reason it's strange not to hear any PS3 fans stating how happy they are Microsoft are investing in their own first party titles.

Everyone thought Microsoft was just dumping teams, but there was a reason. Microsoft got rid of like Ensemble who were great but they were a RTS only studio on a console, FASA which couldn't get games out on time, and ACES which was flight simulator which was only a PC property. In that same time they created the Halo team studio, a Arcade game studio, acquired Big Park and also rumored to have bought the company that have that motion camera technology. Got rid of stuff that didn't fit into there console plans, and picked up ones that did

I wonder, given the experience with mass market games that they will be creating Xbox sports? I.E the next gen equivelent for Microsoft of Wii Sports?

RalliSport Challenge was friggen awesome.

 This. MS won't acquire an untalented studio.

And this game is in development for some years, so this might be pretty big. But we will see.

There is perception, and then there is reality...as you pointed out, M$ is making business decisions to strenghen their gaming position.  As they have been saying for a while, they got alot of stuff in the pipeline, and will share when at the appropriate time. 

I would give up all racing games for another Rallisport Challenge

http://www.joystiq.com/2009/05/07/bigpark-ceo-xbox-360-exclusive-will-broaden-audience-be-playab/

Lemke suggested that his company's upcoming Xbox 360-exclusive game, which has been in development for more than a year, would be in line with what it had released before. Resulting from a fortuitous "meeting of the minds" between BigPark and Microsoft, the game is unlikely to be a typical product aimed at the Xbox's hardcore audience (no space marines here!), instead fitting in with Microsoft's "big push to broaden the audience." A casual, free-to-play title would certainly fit the description, if one were to speculate.

Though Lemke refrained from offering much detail, he confirmed that the "very new and different" title would be playable at next month's E3 -- and that it would break some rules. "[It's] pretty innovative in how it's delivered to consumers," he remarked. And if there's any doubt that the game plays a pivotal role in an audience expansion strategy, consider just what prompts a giant like Microsoft to purchase a Vancouver-based developer that's barely two years old. "It obviously goes beyond one game, right?"