I'm not much of a console fan, to be honest. I've mostly played games on computers, running from C64 -> Amiga -> Windows. Of the current generation, I've somehow ended up with two consoles, though, and have both likes and dislikes for both of them.
Wii - this thing is such a mixed bag, it's not even funny.
The good:
* Innovative controls - I like the WiiRemote, and it works well in various conditions.
* Less intimidation - My wife actually bought the Wii for WiiFit, but will play other games on it as well, as there's less buttons and axis to freak her out.
* Wireless access and Opera internet browser. This is probably the most used feature on the Wii at my house. I just wish the browser could be in 1080 to see text/images clearer. Also, a more modern version of Flash would be nice, but I guess I should be glad I have any, unlike iPad owners.
The bad:
* It has no hard disk, so storing downloads would be a problem, provided it had any larger than some small WiiWare titles and repackaged nostalgia cash-ins.
* No built-in media player capabilities. Would be cool to play MP3 and video off file shares, or even USB. (I believe you can browse pictures off USB, though.)
* Friend codes are a pain in the butt.
* Last gen graphics, with no 720 or 1080 modes. It will acknowledge wide-screen 16:9 480p, but it's still not pretty, especially after looking at either an X360 or PS3.
* Poor control schemes; so many titles don't effectively use the Wii Remote as anything other than a clumsy two-piece joystick. The nunchuck is almost always just used as an analog joystick cop-out or shake-toy.
* Shovelware - Egads! Crap titles abound. Most of Nintendo's own titles are pretty good, but the number of 3rd party titles that aren't complete garbage can probably be counted by the fingers on one hand.
I also have an XBox 360 - it's a little easier to figure out what I like and dislike, here.
The Good:
* Games - a true wealth of great 1st and 3rd party titles. Many at great prices out of the Platinum Collection.
* XBox Live - Good game matchmaking / much easier friending
* XBox Marketplace - Good choices for downloads, plus many free skins and whatnot to change up your menus when you get bored.
The Bad:
* The joysticks aren't best thought-out devices in the world. A quick switch to press (A) button can often result in a bumped (Start) button. It gets less hits as you get more used to the controllers, but it still happens now and then. My thumb is just big enough that hitting the center of (A) also bumps the corner of (Start). I have calibrated myself to hit the right side of (A) but occasionally still miss it slightly and hit center of it. Usually at the most inopportune time.
* The console itself is loud, chunky, and unreliable. RRoD is always a fear in the back of the mind.
* The Microsoft factor. They are a monopolistic company that only provides improvement when forced to. If they're allowed to dominate console gaming, it will likely stagnate like Windows and Office have.