I've been thinking about this today, and I wondered what games could do this. So far I've thought of:

Gran Turismo 5
Final Fantasy XIII
Wii Sports Resort

Wii Fit has so far sold 2.4 million copies this year, in eight weeks. If we were to assume constant sales, that would mean 15.6 million copies this year. Not an entirely unfair assumption, given Wii Fits sales so far. So the question is, are there any other games on the menu this year that could sell this much or more?

I think people are over estimating the sales of Wii sports resort.

Of the games you have listed, Wii Sports Resort is the only one that stands even a ghost of a chance, and that not with Wii Fit having a six month head start.

I think the 2009 sales of FFXIII and GT5 are being vastly overestimated.

FFXIII will not be released outside of Japan in 2009, that is not a question, that is just how things are.
FFXIII Japanese 2009 sales will pale in comparison to Wii Fit sales

GT5 is only rumoured to be in 2009, even if it is, it will be late, and probably won't hit all 3 regions.
GT5 will not come close to Wii Fit's 2009 sales.

Wii Sports Resort is an unknown, we have no idea how much it will sell, and thus is the only game that has a chance

I'm not estimating sales for it, I'm just saying it's a potential contender.

Oh. I didn't know FFIX was being released Japan only... guess I'm not that updated on release dates. And unless something happens to Wii Fit, GT5 doesn't stand a chance, I know that. 30 million PS3, and 15 million GT5 sales? Not likely. Still, are there any other games that can compete?

IF we even see FFXIII or GT5 in 2009... IF we do they'll be out at the end of the year and Wii Fit will have already sold many millions of units. No chance.

Wii Sports Resort?? Although I'm sure it'll become another permanent fixture on the ww Top 5 it would have to create a mass market sensation of it's own to overcome Wii Fit's lead. It's conceivable but I sure wouldn't put money on it.

Wii Sports Resort... if it doesn't come out too late.

StarCraft II will sell more in Korea alone than Gran Turismo and FF will do worldwide.

And The Sims 3 is going to outsell those, as well.

I don't think Wii Sports Resort will. I think if it was titled Wii Sports 2 it would do better. I bet the casual gamer will think its not a normal Wii Sports because of the Resort part.

Back on Topic, if it releases in 09 then Gran Turismo 5. Uncharted 2 will do well on a weekly basis as well.

None.

If Wii Fit manages my prediction (it certainly looks like it will), it will sell

That's

250K/week for the first 6 months = 6.5M

200K/week for the next 3 months = 2.6M

4M for the holiday quarter = 4M

Total = ~ 13M

GT5 would be lucky to get half of those sales in its first 52 weeks. It has no chance. Even if GT5 was released 1st January 2010, Wii Fit could have outsold it for 2010.

FFXIII combined will definitely outsell GT5, but it doesn't really stand a chance of beating 8M in its release year.

Wii Sports resort is chanceless too. It releases Q2 in Japan. Let's be optimistic (pro WSR) and say it has a WW release on the 1st of may. That leaves it 7 months. It also leaves it a gap of 5.5M to catch up to against Wii Fit. It would need to sell 13M in 30 weeks. Possibly more. Now, this is a game that's bundled with an item. To beat Wii Fit, it would have to sell as well as Wii Fit/MKWii did in 08, but in shorter time. Realistically it's Q3 in Americas/Japan. July 1st would leave it 5 months to do what MKWii did in 8. WiiM+ is a harder to produce item than the Wii wheel too. I don't think it can make 10M.

Finally, there's the matter of Wii Play.

It sold 11M in 08. It sells pretty much together with the Wii, and as the Wii will sell a bit more this year, it could easily bump up to around 13M in 09.

I believe Wii Play is the only game that can beat Wii Fit in 09.

MKWii on the other hand, should sell around 9M

(150K/week for first 6 months = 3.9M)

125K/week for next 3 months = 1.6M

3.5M for holidays (5M in 08) = 3.5M

Total: 9M.

So MKWii should beat the 2 first games you listed easily, and possibly Wii Sports resort.

For single-plats, the list is definitely

1. Wii Fit/Wii Play

2. Wii Play/Wii Fit

3. Wii Sports Resort/MKWii

4. MKWii/Wii Sports Resort

After that several titles may take the spot(s).

Edit: I see someone said Starcraft 2, and The Sims 3.

Startcraft 2 first.

Starcraft 1 sold 10M, but over a long period (10 years, but of course not equally much in each year).

PC games are well legged. Not as well as Wii games, but certainily better than X360 and Ps3 games.

So if you expect SC2 to sell 10M, it's doubtfull that it will sell half of that in its first 26 weeks... Very doubtful.

SC2 will probably be around 10th. And saying it will beat the ones in the OP by Korea alone is just silly.

The Sims 3 is essentially the same, but to a larger extent. It is a hugely legged franchise. Now, if you include expansions in the sales, The Sims 3 will have a shot at MKWii/WSR. But of course, you don't.

The sims 2 sold less than 10M worldwide (I think). Needless to say, a very large portion of that was after year 1. I doubt The Sims 3 can manage 5M in its first year, heck, it might not make 3M.

World of Warcraft may very well outsell either of those 2 PC games for 2009, and if an expansion is released, it (the expansion) definitely will.