Netflix - 495 hours
Black Ops- 425 hours
Animal Crossing - 394 hours
World at War - 361 hours
Monster Hunter 3 - 270 hours

1. Super Smash Bros. Brawl - 1221 hours
2. Monster Hunter Tri - 352 hours
3. Super Mario Galaxy - 78 hours
4. Super Mario Galaxy 2 - 64 hours
5. Tales of Symphonia: Dawn of the New World - 47 hours

Zelda Twilight Princess isn't there because I haven't played it yet.... don't judge me!

Here is my top 20, which also happens to be all the games/channels over 50 hours, on the left is what I calculated from adding up all the "today's achievements" postswhich I have been doing for a while now (I continued doing it when the Nintendo Channel started tracking time as a number of games were not included on the channel). on the right is the time displayed on the Nintendo Channel, which in some cases is slightly different (presumably I made a mistake adding up)

 The Nintendo Channel and Shop Channel are only so high because I collect data from them weekly/monthly.

Holy crap!  You actually added up all the daily messages on playtimes also.  Your dedication to determine your play time amazes me. 

Since my Wii died and got replaced not too long ago I don't have the real time but I know Brawl wins by a landslide with around 500 hours of power time and 400 hours of play time.

@d21: How did you manage to play Wario Ware for 78 hours? I'm shocked, once I went through all the mini games I thought there wasn't that much to do.

The first time I did it (after about 10 months of owning it) it made me realise how much time I was spending on the internet channel, which made me try to cut that down (although a few months later it became very difficult to post anything on VGC with the Wii browser so that would have stopped me anyway) About 600 of those internet hours were within the first year.

As long as you were using the browser for VGC then that puts you in better standing.   However, if you check out horn dog d21lewis' browser time and his other posts...  I believe he was using his Wii internet browser to play with his Wii.

(Can't quote)
@TruckOSaurus We're Warioware Maniacs at my house! Plus, whenever anybody wanted to see the potential of the Wii Remote, no game conveyed "what could have been" better than that game (Just like it did with the DS with Warioware Touched).

But, man. Looking at the other people in this thread, I wonder if I'm even worthy of owning a Wii. I thought I'd used it quite a bit! Next thing you know, people are going to tell me that my four inch penis is below average, too (As if!)!! As this gen winds towards its conclusion, I find myself going back and playing my Wii more often. The flash and online of HD games have begun to grow old and I long for more traditional experiences, even if they lack graphical punch. I'll get my Wii Numbers up, starting with a replay of Metroid Prime 3 and SMG2.

Final Fantasy III (VI): 40hours, 27minutes: Played 13 times
Little King's Story: 34h 16m 18 times
Chrono Trigger: 27h 51m 23times
Grand Slam Tennis: 24h 54m 21times
The Legend of Zelda: 22h 47m 16times

Super Mario Galaxy 2 just missed out.
I don't think this is totally correct though. It says iv'e only played Wii Sports resort 4 times, when I have played it much more than that.

Holy crap. Compared to a lot of you, I don't play very much.  Which is crazy because my play time on most of my games is double the average on the Nintendo Channel.  I'll start with Netflix, but I made it number 0 since it isn't a game.

My actual time/Average time of users on the Nintendo Channel

0. Netflix: 219 hours 34 minutes / Average 74 hours 13 minutes
1. Super Smash Bros. Brawl: 94 hours 20 minutes / Average 80 hours 47 minutes
2. The Legend of Zelda Twilight Princess: 86 hours 39 minutes / Average 48 hours 11 minutes
3. Super Mario Galaxy: 77 hours 36 minutes / Average 32 hours 26 minutes
4. Tiger Woods PGA Tour 10: 73 hours 32 minutes (and still playing!) / Average 24 hours 52 minutes
5. Muramasa: The Demon Blade: 55 hours 10 minutes / Average 13 hours 50 minutes
6. Wii Sports: 54 hours 21 minutes / Average 41 hours 35 minutes
7. Mario Kart Wii - 51 hours 42 minutes / Average 44 hours 32 minutes
8. Metroid Prime 3: 47 hours 2 minutes / Average 22 hours 25 minutes
9. Wii Fit: 45 hours 54 minutes / Average 23 hours 44 minutes
10. Call of Duty Modern Warfare Reflex Edition: 43 hours 13 minutes (and still playing!) / Average 60 hours 57 minutes

Zack and Wiki, Guitar Hero 3, Okami, No More Heroes, and de Blob are all in the 30-40 hour range.

Metroid Other M, Wii Play, NSMB Wii, Boom Blox, and Wii Shop Channel are all in the 20-30 hour range.

A Boy and His Blob, Excite Truck, Internet Channel, Metal Slug Anthology, Ghostbusters, Nintendo Channel, News Channel, Overlord Dark Legend, Cursed Mountain, Tetris Party, DKC Returns (still playing), Wii Fit Plus (still playing...occasionally), Art Style: Orbient, The Munchables, Toki Tori, and Check Me Out Channel are all in the 10-20 hour range.

Everything else I own is below 10 hours.

With the exception of a few of the games below 10 hours and the games I am still playing, I have beaten everthing on this list.  Usually to 100% complete.  Some of these games I beat more than once.  The times listed here are pretty much all me except for Super Mario Galaxy.  My friend played that one, so it is probably about 40 hours that is the actual time I spent with it.

EDIT: Numbers updated with the actual figures.