Great idea! We still have a super nintendo that my 8 year old loves to play. Mario, Donkey Kong Country 1 and 2 - it's great :)
My Super Nintendo is still holding up, but pretty much every old original NES I've seen hasn't aged very well. Something with the mechanism that holds the cartridge fails over time, and you can't get the system to work anymore.
Also, now that they're using disc technology, it's more likely that the next few generations of consoles could be backwards compatible with old games, meaning that putting the classics on a disc now would mean that you could play them on the newest system out until disc technology itself is replaced or substantially altered.