Well I voted all 3. Last year's E3 wasn't the best for any of the companies, so I really think they ALL will have something to impress with this year. Nintendo and Microsoft in particular because we know so LITTLE about what they have coming, but Sony too because what we know they have coming should impress much. Plus this is the RETURN OF E3, so all of them are going to want to impress and inspire.
Sadly, the polls on this site only reinforce how strong the fanboy community is here, particularly for Sony. I'm an owner of only a 360, but there was no way I could vote for MS no matter how excited I am about their showing. I'm a gamer first, and I imagine that this E3 will make folks like me truly wish we could own (and have time to play) all 3 consoles.
