(OPINION) This is a hard choice. For me I'd pick the Wii. I am not calling it my favorite console ever but it changed a lot in the industry. Who knows where motion controls would be today, or if they'd even exist. A close second would be the NES, since it saved the gaming industry in America. Sega Genesis would be my 3rd because it ignited console wars, and who knows if companies would've really been brave enough to face Nintendo if it weren't for them. N64 comes 4th because of the fact it had an analog stick and PS2 is 5th because of huge sales and really showing off great 3rd party.
XBOX ONE/Wii U/3DS/PC
RIP Iwata 12/6/1959-7/11/2015
Thanks for all the great memories!