PS4, Wii U, PS3, and PC. Off to the sides to be plugged in if ever needed is the Wii and Xbox 360. So, four at any given point. I'm mostly a handheld player, so that's where the majority of my systems exist.
Xbox One in the family room. PS4 in daughter`s room also has Alienware PC in there. PS3 and 360 in other daughter`s room also has Alienware PC in there . Have a Wii not connected somewhere. 2 3DS units.
My PS3, PS2, and 360 are sitting in my garage at the moment. I moved in September and haven't unpacked those items. I gave away all of my older systems during that move and do not own anything newer.
NES
Famicom w/FDS
N64 w/ 64DD
Gamecube w/ GB player
Genesis
Saturn
PS2
PS2 TEST
XBOX
SNES is waiting on an RGB cable due in soon, dreamcast needs a replacement cd drive, and the cdi is probably going to stay unhooked until the day i feel like i really need to play it again which is pretty likely to never actually happen.
Also in the living room I have a 40" Sony Trinitron CRT for any older systems, but right now there's only:
Slim PS2 (w/ component cables)
In the kids play room:
Fat PS2 (mostly so they can watch DVDs on the rare occasion they want to and can't use any of the other TVs)
In my bedroom I just moved in the 32" Vizio LED that was my main TV until recently. I spend very little time in this room but I'm going to get a Vita TV for it sooner than later. It's still a very nice TV, only a couple years old and great for gaming (very little lag, great picture)
PS4
PS3
XBOX ONE
Xbox OG (Only used for emulators NES SNES Genesis Oh and I guess I do play the Bible Game on it. It is my favorite party game)
WiiU
PC
In the living room we have a PS4, PS3, 360 and PS2 hooked up and I have a Genesis, PS1 and N64 hooked up to a tiny CRT on a nightstand in my bedroom.
There's a Saturn and a snes in my closet that I wouldn't mind hooking up, but they're both busted and my current library for them is super anemic. Oh and we have a OG Xbox hooked up in the family room, but the tv that it's plugged into has water damage from when our roof leaked during a storm last fall.
I have three hooked up: 360, WiiU and PS4. My dead PS3 is still hooked up to my tv just because I haven't got rid of it yet :[ rip. And my pc, but that's hooked up to a monitor on my desk.
If I had a bigger apartment I would bring out all the old systems I own. I still have every Nintendo system from NES to Wii in storage. PSX and PS2, and original XBOX also boxed up. Genesis and Dreamcast as well. Just too much effort to get them all connected.
I have...21 systems hooked up to my main TV, a Sony W900A. Those are:
NES
Genesis/SegaCD/32X
Super NES
3DO
Atari Jaguar
Playstation
Saturn
Dreamcast
Nintendo 64
Playstation 2 (launch model)
Playstation 2 (slim model)
Xbox
Gamecube
Panasonic Q
Xbox 360
Playstation 3
Wii
Wii U
Playstation TV
Playstation 4
Xbox One
All of those except the last 3 are also hooked up to my Sony WEGA, and an Atari 2600 and extra Gamecube are hooked up to it also.
And I have an extra NES, SNES, and Genesis hooked up to a very old tube TV for light gun games.
So that makes...26? And 2 PCs (Win98 and Win7). So 28, I guess.