My guess is Wii Play, mostly because Wii Fit is going to divebomb in sales, or at least seriously slow down once Wii Fit Plus comes out.

If you don't count those because they are bundled with stuff or aren't "real" games, (poor reasons), and then don't count handheld games, probably Mario Kart Wii. Now if THAT's not counted because it comes with a wheel (crazy, but I've heard people make that argument), I'd wager New Super Mario Bros Wii. Now if you don't count THAT for some reason, you're really grasping at straws.

Of course, there's always a chance for something to come completely out of left field, most likely on the Wii. For all we know, the vitality sensor game will become a huge hit (I doubt it, but...)

I also get the feeling the best selling title will be a Wii Series game. Their sales numbers are simply too high to be denied. But should a future title come along and shake things up it will need to have the same across the board appeal as games such as Wii Fit and Wii Sports.

Wii Fit will be the best SELLING game.

Well, I believe you should include Mario & Sonic @ the Olympic games, if you're including CoD 4 and GTA IV. It's at 11.23M and 1.1M of those are as of this year. It should definitely reach 15M, which is more than CoD 4 will reach, and roughly what GTA IV will.

Probably Wii Play. That game has been out since Wii's launch and just keeps selling, whereas Wii Fit will probably see lower sales once Plus is released.

Most likely Wii play or Wii sports resort. Wii fit plus is pretty much an upgrade of wii fit so there is really no reason for a consumer to buy regular fit over plus unless wii fit is cheaper by a significant amount. So I think most of us realize that Wii fit plus will still most of wii fit's sales.

Wii sports resort came out strong in japan, but we will have to see what it does in the rest of the world to judge if this is the next big Wii series game.

Wii play because it is already done amazingly well and continues to have a high attach rate.

Most copies distributed: Wii Sports
Best selling game with controller/peripheral: Wii Play
Best selling game without controller/peripheral: Nintendogs

Wii Sports

New Super pokemon wii sports party 4: tursimo version

With the way Wii Sports Resort is selling in Japan at launch I wonder what kind of numbers it will produce in other Regions. This game is likely gonna have a huge launch and if it has legs it could rank as of the top selling games of this gen. After playing it I got a strong feeling about this title.