While the Sega Master System may have had a longer lifespan in Brazil, I have unearthed no evidence that cartridge-based consoles were manufactured for a continuous twenty-year period. Moreover, Nintendo also holds the record for hand-held systems. Nintendo released the Game Boy on April 21, 1989 and only discontinued its Game Boy Advance (which is backwards compatible with Game Boy and Game Boy Color games) in 2008. As Game Boy games are region free, that copy of Super Mario Land purchased at launch would still work in the last Game Boy Advance SP handheld systems sold in North America in 2008.
However, Sony's PS3 is still in production and Sony has stated that it will support it at least through 2015. Even today, the PS3's backwards compatiblity with PS1 titles has eclipsed Nintendo's media support. Playstation games have seen continuous support since 1994 even if the consoles were last manufactured in 2004, because they will work on Playstation 2s and Playstation 3s.