While I could see putting Nintendo's total booth on par with Xbox's booth, I think it's a pretty big insult to say Gamecube's showing was equivalent to Xbox's. I certainly didn't think much of MS's booth, but they've still got 3rd party support almost as good as PS2 and they have an extremely strong lineup. Gamecube had my game of the show RE4, the suprise of the show Zelda, and MP2 looks good, but beyond that there wasn't much. As they said GC third party support was nearly non-existant plus there's still no online support.
Xbox on the otherhand had the entire EA Sports catalog on Xbox Live, FSW, Riddick, Doom3, Republic Commando, MK: Deception, DOA Ultimate, Halo 2, Jade Empire, KOTOR 2, PSI-Ops, Mercenaries, Pain Killer, Call of Duty, Far Cry, Fable, Men of Valor, Iron Phoenix, DDR Ultramix 2, Burnout 3, SNK Vs. Capcom Chaos, Advent Rising, Area 51, Conker, Mech Assault 2, Battlefield, Silent Hill 4, SW: Battlefront, Kameo, Dead to Rights 2 and on and on with support in almost every genre from 3rd parties. Almost every single 3rd party game I look into is now only for PS2 and Xbox or Xbox and PC. No way is Xbox's lineup at E3 equal to that of the Gamecube's. I'd rate Nintendo's showing better than Microsoft's because of the DS & a better booth, but no way can they give that much credit to Gamecube. 3 great looking games for Gamecube can't make up for a complete lack of 3rd party support.
I agree that Sony was much better though. Even not counting the PSP they dominated the show with the PS2 lineup and had the biggest booth. When you count in the PSP which was the most impressive thing at E3 they won by a mile.
Also asking if GBA is on the way out? That's just stupid. Nintendo is adamant that the Gameboy line and the DS line are intended to be two completely seperate platforms. The DS is not even going to be able to play old Gameboy games like the GBA can.
It always amazes me how wrong EGM is at accessing E3 every year. Do they spend the entire 3 days in meetings and end up missing the real show or what? Whatever they're doing it's not working for them at all. I remember when they came back from E3 completely overlooked Splinter Cell and said that the MGS Substance port was going to be the biggest game of the year for Xbox.

They also thought Mario/Metroid/Wind Waker were going to completely crush the Xbox that year.