I know someone that knows him, and she says he is very competent and a great guy.  Here is his CV (scroll down a little), though it may be abbreviated, but it doesn't mention PG.  Ballmer's CV does mention PG.  Immelt is now, later in life, on the Board of Directors at PG.  That came up on a search of his name with PG.  So the honest answer is I don't know, but if I had to guess and bet, I would assume that Immelt went directly from his MBA to GE, as GE hires MBA's and loves to grow their people from the ground up, and they might have mentioned that in the abbreviated CV (though maybe not).  And his current Board seat at 50+, might on an Internet story be associated with Ballmer working there in his 20's.

But I'm just thinking through the people I have been associated with in my career, and thinking how I would be judged using the same type of comparison--I guess it's OK, except for that one guy who was an ax murderer.