The way I see it, Microsoft has Halo 3 for the next year. Which is going to be a momentous event in gaming history, even if the single player sucks (again). Over at Gamefaqs Halo 3 was voted the most anticipated E3 game, so a big chunk of the gaming public are looking forward to that.I'm slightly biased towards Nintendo's conference because I was sitting in it, but...
I haven't seen the other conferences yet. I was told Microsoft basically showed off everything they had already, and Sony announced some new exclusives and a nearly-indistinguishable slightly thinner PSP with a TV out.
Sony vs Nintendo really. The new exclusives are a big deal, but are mostly catch-up for previous mess-ups.
I'll go with Nintendo, but I admit that having been there I probably enjoyed it a lot more.
No hardware from Nintendo.