This is a rough estimate, but here's the ballpark of what I've been playing (these are just the times I regularly played these consoles, doesn't consider the times I'll still occasionally pick them up):
1989 - 1995 NES, (3 - 9 years old) - I still played Mario 3 and Bubble Bobble well into the life of the Super NES
1989 - 1993 Atari 2600 (3 - 7 years old)
1992 - 1998 Super NES (6 - 12 years old)
1996 - 2002 N64 (10 - 16 years old)
2001 - 2004 Gamecube ( 15 - 18 years old)
2002 - 2005 Dreamcast (16 - 19 years old)
1991 - 2004 Gameboy/GBC/GBA
late 90s, 98-99? Gamegear
2005 - 2009 DS, though I will probably pick it up again soon once I get DQIX and Pokemon Black/White
2005 - present Xbox 360 (19 - 23 years old)
2006 - present Wii (20 - 23 years old)