NOA vice president George Harrison confirmed that downloading classic NES, SNES and N64 titles on the Revolution will be free.

I dont understand the reasoning behind this…but I cant say Im complaining. I love free stuff. That said though, I know that many people, myself included, would pay a small fee for each game. Nintendo will also have to be careful as to how many games they are offering so that people dont simply play old games and not buy any new Revolution software.

Games Radar Article

EDIT: There are concerns that this info may not be true and that Games Radar may have just been making an assumption. Ill try to find out the truth as soon as possible and let you know.

Here is exactly what was said. Take from this what you will:

Gamespot: Do you plan on having like a per-download pricing model along the lines of the microtransactions that will be used in the next-gen Xbox marketplace?

George Harrison: Well, we can use it in a variety of ways. We’ve used some of the older games already as little bonuses, either as bonus gifts or hidden in levels of games. Certainly for the first-party titles we’ll be making some of those available. We haven’t really talked about whether we would sell them. The third parties can make their own decision whether they want to sell them, or maybe they will add it on as sort of a free benefit when you buy a current version of the game.

source: Joystiq