And like somebody already said, Nintendo was far worse. Third parities weren't allowed to make Nes games that competed directly with Nintendo's games. They could only produce a certain number of games per year. They had to buy a certain number of cartridges from Nintendo to put their games on before the game released. They couldn't release the same game for competing platforms until after a year had passed.
This continued until the PS1 era. When Sony started kicking serious ass, that's when Nintendo learned a little humility. Thing is, Nintendo third party support has never been the same, since. And, while I don't have anything to support the assumption that Sony made a similar move, I recall a few bigger games getting early release on PS2 (MGS2, GTA3) while, at the same time, games like Splinter Cell would get released much earler on Xbox. Maybe, to a degree, everybody is guilty.
