I'm not sure who they are and it has been nagging me for quite a bit.  My guess is..

EA
Activision/Blizzard
Ubisoft
Sony Computer Entertainment
Capcom

Please correct me if I'm wrong.  Also thanks in advance.

what's exactly you definition of a big publisher ? Number of games ? Number of AAA games ? Number of games sold or published ? Number of employees ? Revenue ? Profits ? Do we consider hardware builders too ? And multimedia groups ?

 Nintendo should be at least in the top 3.

So you has to remove one, which would be Capcom I believe.

How can you have Sony but miss Nintendo? Are you talking about profitability or who produces the most? By profitability it'd be something like:

Nintendo
.
.
.
.
.
.
.
EA
Activision
Ubisoft
Sony (or maybe Capcom/THQ/MS/Sega)

 Revenue of course.

I was talking about employees within the company.

I think he means in terms of sales, in which case there are a bunch of companies you're forgetting. Take 2 would definitely take Capcom's place if nothing else.

EA is unprofitable right now (...), so they'd be below Ubisoft but above Sony.

And in terms of size, I think Activision is first, but I'm not sure who's after that, especially in light of all these layoffs.

I think your list is fairly close to accurate, but I would think Nintendo (including all their studios like Retro) would be bigger than Capcom. But I really don't know.

Nintendo definitely up there in terms of sales, actually they would easily take number 1. In terms of people SE have 3.2k employees according to wikipedia, do not find that hard to believe seeing how many games they release per year.