If you have a pair of 3D glasses in the house, go get 'em, then settle in and see what it'll look like when Nintendo starts to raid its back catalogue and re-release old classics on the 3DS.
This is Mario 64 and Starfox in 3D. Well, it will be when you click on the vids and actually watch them on YouTube; for some reason, the 3D effect can only be triggered on their site, and watching it here will just show two clips running side by side.
Those without glasses, you can get a similar - if painful - effect by watching the videos here, then going cross-eyed. It works! But it hurts.