Wii and DS Lite for me. Been giving thought to picking up a PS3, but not ready to make that jump yet.

NES
SNES
N64
Gamecube (w/ Gameboy Player)
Wii

Gameboy
Gameboy Color
Gameboy Advance

Virtual Boy

DS (x2)

PS2

Xbox
Xbox 360

Game Gear

I have a 360, DS, Wii & PS3. I play a 360 and DS.

I have, in order of play frequency:

1) 360
2) DS
3) [too much of a gap to actually put the Wii as 3rd]
4) Wii
5-8) [same as 3]
9) Couple GBA:SPs for DQ1-3
10-tie) N64 (not even hooked up)
10-tie) PS3

I haven't played a single PS3 game and I've had it since August or September.

Wii
PS3
DS
PS2
Gamecube
SNES
N64
Coleco

There is no longer a functioning NES in the house. So sad.

In order of most played

360
PS3
PSP
original X Box
PS2
Wii
DS

Wii
360

I also checked "Previous Generation Handheld" because I have a TurboExpress but I never play it.

Currently playable (they're hooked up and ready to play).

360
Wii
Xbox
PSP

I have a PS2 that could be hooked up in pretty short order. I swapped out the TV it was hooked to, and never hooked it back up.

Geez I checked everything but Gaming Mac and Other.

Currently in possession of:

PS3 60GB circa 10/07
XBOX360 circa 01/08
Wii (launch)
PS2 (circa 03/02)
GameCube (launch)
PSP (slim-silver)
DS (launch)
Gameboy SP
Gaming PC (getting a little long in the tooth - P4 3.0Ghz with BFG 6800GT)

Here's what I still have hooked up and still play, with an approximate percentage of how much of my (5 hours a week) gaming-time is devoted to each.

360 - 55%
PS2 - 15%
Wii - 10%
DS - 10%
PSP - 5%
Dreamcast - 5%

NES
SNES
N64
PS2
GameCube
DS
Wii
XBOX360