Atari 2600 - this is what made video games popular. Has a huge game library and lots of history, a very interesting system to investigate the life of
NES - this one brought the video game market back, in the USA at least, and made a lasting worldwide impact. Huge game library as well, many first-rate titles (some AVGN fodder as well)
Sega SG-1000 - This one started Sega out. There's just something so lovable about this little system.
Sega Genesis - my first ever console
SNES - what a great system!
PlayStation - the console I grew up on
Nintendo 64 - the first ever console I played, with Super Mario 64 in fall 1998
Dreamcast - the system denied a chance at success
PlayStation 4 - we get our TV through it!
Casio Loopy - this one gets in solely on its craziness
So many I had to leave out, such as Sega Master System and Saturn, PlayStation 2, Xbox 360, the fully backwards compatible PS3 (all PS1, PS2, and PS3 games can be played. That's a HELL of a library)