This is a tough year, mostly because I don't think anyone is amazingly strong.  Also even the ones that look kinda strong are not making games really for me. Here are some contenders:

Take Two, Sega, Nintendo, Microsoft, Capcom, Konami - All of these studios have a solid lineup of games, but I've never played hardly any of them.

EA - This would look more impressive if The Sims were a new game, but it actually wasn't new at this point.

Squaresoft - FFXI and Kingdom Hearts.  They only have two games, but I really love them both.

I'm going to have to give this one to Squaresoft again.  IMO, they can do no wrong at this point in time.  It's merging with Enix and Sakaguchi leaving that really screwed them over later.

Yeah, sadly when I'm going through history I can't literally check how each game was shown off (meaning if it was brand new or just more shown off than before). That would probably make this take 10 times as long to compile and it already takes a long time for me as I have to check individual games out to see who was the main developer behind it and who owned that deverloper during that E3. 

easily Nintendo

Animal Crossing
Mario Party 4
Metroid Fusion
Metroid Prime
Pokemon Ruby/Sapphire
Super Mario Sunshine

Metroid Prime makes it an automatic win for Nintendo. 1080° White Storm, Eternal Darkness: Sanity's Requiem, Mario Party 4 and Metroid Fusion are just icing on the cake.

That is an impressive lineup from a hardcore perspective (of which I fall in that camp). Sadly, OG Animal Crossing, Fusion, Prime, and Sunshine fell outside of mainstream view.

I’m going to be the second person to vote Sega because we Skies of Arcadia fans need to express our love if we’re ever going to see a re-release.

Yep backing SEGA here

17 votes so far with Nintendo winning currently!

Lools like Nintendo wins this one based on voting so far.