I dunno, I'm familiar enough with these kinds of deals to know they always involve money... Mostly marketing support. For time exclusivity. Ports don't mean anything after a set marketing period, the partners get the ROI they are targeting for the marketing support and the content producers get the revenue of the later platform after.
Parity clauses usually have an expiration date.
So, money.
That's how it usually works, but apparently not this time. Moneyhat wasn't the primary motivator for Resident Evil's exclusivity, and contracts apparently didn't apply to the Capcom 5.
http://kotaku.com/5968398/why-resident-evil-4-became-a-nintendo-exclusive
http://www.eurogamer.net/articles/2012-12-13-why-xbox-failed-in-japan
Microsoft "heard through the grapevine" that Mikami was upset with Sony, so they tried to win him over. Mikami confirmed to Microsoft that he was upset with Sony, and he was just looking for a plausible excuse to move Resident Evil away from them. Then Microsoft screwed up, because Mikami asked what Xbox's philosophy was, and none of the MS people in the room knew if Xbox even
had a philosophy. So Mikami was left with only GameCube as his escape from the PS2.
http://ca.ign.com/articles/2002/11/13/capcoms-fantastic-five
http://ca.ign.com/articles/2002/12/10/capcom-on-gcn-five-exclusivity
http://ca.ign.com/articles/2003/01/16/cgd-03-capcom-five-not-gcn-exclusive
For the Capcom 5, Mikami had the authority to greenlight games, so he (having already hitched his wagon to GameCube and being under pressure from Capcom and having a stake in GameCube's success or failure) greenlit four more games for GameCube. One month after announcing the games, people were asking what exactly they meant by "exclusive", and one month after that, Capcom clarified "not exclusive". IIRC, Mikami later said that he meant "exclusive" as in, he greenlit these games for GameCube, and nobody had yet greenlit them for anything else. And if a game is only available on one console, then it's obviously exclusive.
Three months later, Mikami was demoted/stepped down.
One year later, Viewtiful Joe made the jump to PS2, and another shitstorm exploded, and Mikami said it's no big deal, because the Capcom 5 (minus Resident Evil 4) never had any contracts, and were not really exclusive. But RE4
was exclusive, and would never be on PS2!