The US ads are probably going to be lame. I suspect a "Wii would like to play" style which is really the exact opposite direction Nintendo should go for this game in particular. Sonic and Snake (and any other 3rd party character(s) they have planned) should also be shown (edit)...... even if they're unlockable characters. Sure, it spoils the surprise, but it's sure to drum up even more buzz for the game.
On a related note, the US ad for the original Smash Bros. was probably Nintendo's best commercial ever.