I will also steal CGI's format.

2nd

(Wood Grain bitches)

3rd

4th

5th

6th

7th

( I guess.  My PS3 has more hours of use this generation.... but it's mostly PS2 games.  So make of that what you will.)

PS1
PS2
PS3
Yeah I'm boring but I have owned an N64 and Wii and played extensive GC and 360 at a friend's house in their respective gens. I also played a lot of Sega Saturn but was meh on every game I played on it.

Nintendo

NES
SNES
N64
Gamecube
Xbox 360
Wii U

I loved the Wii very much though

Main: PS1
Main: PS2 support: Xbox, GameCube
Main PS3. (Also had a 360 and wii at some points but the ps3 was more then enough)

if you view it like that, given by how many games i bought for each console yes you could say i have a main console, but that is not how i view it i view by how much fun i am having while playing my consoles/PC i only buy good games so by that logic i have had the same amount of fun from each of the consoles i have owned.

an example:

in the PS1 and N64 Era there were a lot of games for the PS1 while there were not quite as many for the N64, but i had an equal amount of fun from both consoles, they saw an equal amount of use.

Nintendo Entertainment System

Nintendo 64

Nintendo Gamecube

Xbox 360

Wii U (I expect to use it more than Xbox 3.)

2nd gen - Atai 2600
3rd gen - Commodore 64 (not sure if thats strictly 3rd gen but thats what I had)
4th gen - Sega Mega Drive (but equally liked the SNES)
5th gen - Playstation
6th gen - Playstation 2
7th gen - Playstation 3

All consoles have great games. That isn't what is asked. What is asked is which console did you game the most on. Regardless of the quality of the fun you had on them.

-N64
-tie between ps2 and gamecube.
-PS3