Well, from a system-selling standpoint, Mario Kart 3DS and Ocarina of Time 3D would do wonders. I know I'd have to get both at launch. It's a perfect mix for gamers, with your arcadey multiplayer fun on one hand, and your sweeping single-player epic on the other.
With the framework to OoT already existing in the N64 original, it's mostly a matter of updating the art assets/sound samples, implementing 3D and touchscreen item selection, plus any other bells and whistles they plan to include. And for Mario Kart, they can crank out another one of those like nobody's business. They have it down to a science after MKDS and MKWii.
Mario and Zelda at launch... How amazing that'd be if that rumor panned out to be true. If nothing else, I hope Wednesday's conference brings us a trailer for OoT 3D. The screenshots look gorgeous; a graphical facelift is exactly what this classic needed, and in stereo 3D, no less.
Of course, Kid Icarus certainly seems poised to be a launch or near-launch title, and that'd certainly bolster the franchise's standing. It's mostly hardcore gamers picking up new systems at launch, so what more fitting tribute to fandom than the new Kid Icarus? I'd hazard to guess that Steel Diver, Nintendogs + Cats and Pilotwings Resort are first-quarter locks. Pilotwings in particular seems like it'd be an excellent title to bundle with the system... With its ties to the Wii Sports world, and its user-friendly controls and immersive sense of 3D, it seems like a perfect pack-in.
Man, speculating how the 3DS launch will shake out is so much fun.