Actually, I researched this last night trying to figure out why Sony didn't pull the Rumble Pak as prior art, or why Nintendo has not been sued by Immersion. What I found only left me more confused.
Patent
6,200,253 [uspto.gov] is Nintendo's Rumble Pak patent, which came out over a year before the Immersion patent. The thing is, it specifically talks about being a detachable device. The GameCube controller's rumble is built in, so it would seem to fall under the Immersion patent. However, maybe they have some sort of private agreement not to sue since Immersion would likely lose their patent.
Patent
6,743,104 [uspto.gov] is Nintendo's patent for rumble in Game Boy cartridges. This patent references both their Rumble Pak patent as well as the Immersion patent.
It's also interesting to note that something like a dozen Immersion patents specifically reference the Nintendo Rumble Pak, Sony Dual Shock, and sometimes the Sega Jump Pack. Clearly Immersion was well aware of force feedback devices and who was actually using them. I'm not sure what took them so long to try to make a claim on it.
All that said, by the manner in which the Immersion patent in question reads, they pretty much patented every possible alternate configuration of a force feedback/rumble device (different housing, different actuators, different shaped eccentric mass, etc). In being so general however, you'd think that vibrators would be prior art as the first sentence of the patent reads "A man-machine interface which provides tactile feedback to various sensing body parts is disclosed."