More important than the end of hardware production (or the official announcement of the discontinuing) is the end of software support (IMHO).
So in which year did these systems get their last good first party games* and in which year did they get their last good third party games*? How many good games were released in the last two years of the system?
* new games, so no late ports or late translations or game collections
For example: even if the NES was discontinued in 2003... it wasn't supported from Nintendo after 1994: http://www.gamefaqs.com/company/1143-nintendo?platform=41&year=0®ion=0&devpub=0
The last Nintendo-published NES-games were Wario's Woods, Megaman 6 and Zoda's Revenge in 1994.
PS2 got its last retail release in 2014: http://venturebeat.com/2014/02/02/playing-the-last-playstation-2-game/
Here is a good article about "swan song games": http://www.usgamer.net/articles/system-swansongs-the-last-games-released-on-the-greatest-consoles
