Wii: Price of games. Take the latest COD, the Wii version was like £10 more expensive than the HD versions. It's clearly cheaper to make the game, bring the price down.
Online. Don't mind friend codes too much, bit of a pain, but I can live with it. What annoys me is the fact I don't know what any of my Wii friends are doing online. Would be nice if I could view my friends list and it says "X is currently playing Mario Kart" etc.

Wii: Some games I have are pretty much GC ports. Most games on it have pretty much been confirmed that playing with the GC controller is better than the Wii-mote nonsense. I don't like solid gameplay broken up with excersize routines in an attempt to justify the presence of a wii-mote (i.e. they would be lambasted by reviewers/fans if they weren't to include some functionality)

XBOX360: Threat of RROD that lingeres and the super annoying fact that for some reason Video clips/DVDs will not have the sound work on them from time to time. I'm assuming this is a codec error, but it doesn't make much sense to me. True arbitrarily the sound will comeback after "reboots" but it just is something that shouldn't be.
Also I prefered the original blades to the new look.

Wii: Lack of memory

Xbox 360: Too noisy

DS: No complaints here

Wii:

1. The PAL Wii has the 50 Hz version of most of the VC games, and I simply cannot understand why Nintendo did this. One thing was that we had NES games that run 20% too slow with big black borders and thus a slightly wrong aspect ratio 20 years ago, but that we still have to live this today???

For this reason, I sold my European Wii that I bought at launch and imported one from Canada. Now I get all the games in proper 60 Hz, + the games are cheaper :)

2. Lack of storage space. Mine is completely full with VC and WiiWare games.

3. Internet service is too slow, takes too long to connect to Wii Shop etc, and takes too long to find opponents in games like SSB:B.

4. FRIEND CODES - BLAH!

DS:

Internet service is too slow, apart from that, it's mostly good, would have liked some internal storage space and a built-in, WORKING web-browser (Opera on DS is terribly slow and unusuable), but I guess the processing power simply isnt enough.

Edit:

Oh and another thing with the Wii. For the NES games you cannot map the buttons on the controller yourself. Playing a NES platformer like Super Mario Bros with the classic controller is almost impossible, because you have to use the classic controller's B button for running and A for jumping, where it should have been Y for running and B for jumping with the SNES-like layout.

This means that the only way to play those NES games somewhat easily is to use just the Wii remote, which is not very comfortable to hold sideways (and the classic controller has a better D-pad). The GC controller is not an option either as the GCs d-pad is completely useless.

Huge oversight by Nintendo, I wonder how they can make simple mistakes like these...

2nd edit: When your Wii is set to 16:9 mode, the Virtual console games who are all 4:3 should have been automatically letterboxed with black borders on the sides so you got the correct aspect. Annoying to have to switch that on my TV manually.

Wii:
-Games look clunky on close inspection when played on a Philips 42in HDTV (1080p). Maybe it's the upscaler.
-SNES games like DKC2 are made way harder when played with the Gamecube controller.

DS lite:
-The Slot-2 is not optimised for the GBA cartridges!

 What? Whereever I look, Wii games are cheaper than XBox 360/PS3 games by like 20€ usually.

PS2: inferior graphics compared to GC
GC: lack of deep games, lack of USB ports, lack of third-party titles, lack of buttons on the controller
X360: red ring of fucking death

kylohk, do you have the Component cables or the standard RCA?

When I bought the component cables the visuals were much clearer as well as the contrast ratio

(I also have a Philips 42" HDTV) Ambilight 2 to be exact.

Hmmm...

X360: it's loud.
Wii: Can't turn it on with my universal remote.
PS3: Can't turn it on with my universal remote unless I keep a USB dongle in it that makes the controller always default to player 2.

360 - the fact that its broken twice

ps3 - No backwards compatibility.