IGN posted an interesting article about the 5 consoles with the longest lifespan (from when they release until they are discontinued). As one of the comments on the site say, it's interesting how none of these would really be thought of if posed with the question of which console has been around the longest:

5: Super Nintendo Entertainment System/ Super Famicom (13 years)
4: Nintendo Gameboy (14 years)
3: Atari 2600/ VCS (15 years)
2: Nintendo Entertainment System / Famicom (20 years)
1: Sega Master System (28 years and counting!)

1: Try to wrap your heads around this: the Master System hit shelves in 1986 and it never came off them. That's right, you can buy a 28 year old console brand new.

... In Brazil.

See, the Sega systems got really popular in Brazil, so a local company called Tectoy was licensed to keep on producing them long after Sega discontinued them. It's not just the Master System - Tectoy also produces new Genesis consoles. Turns out they've really tapped a budget/ nostalgia market and both systems get de-makes of recent games like FIFA '08 or SimCity (and a 16 bit Guitar Hero). Granted, these entries are a little debatable because the consoles come pre-loaded with games and they are different from the originals. Because of this ethical cesspit, we're not including the Genesis on the list (which would have been #2 at 26 years).

And while it isn't exactly the same console we know and love, isn't it a little heartwarming to think that you could play Sonic or Phantasy Star on a brand new Sega?