Gotta love the NES. I had seen a few designs around here, but none of them color-printable. So after a few trial-redesign rounds, here is the final result :)
1) Print the body in white, A+B in red, and cross+start+select in blue/black.
2) Assemble all the buttons, you can use soft foam to make them "press-able".
3) 2D print the sticker (if you happen to have one of those rare 2D printer), plastify it, cut the holes with an X-Acto knife, and glue it in place.
4) You can also put a cable with a connector to make it even more realistic.
Design made in Sketchup. Again, I'm sorry for that. Summer is near and I will learn OpenSCAD soon.