I agree with Source on this. I see Halo 3 in the 7-11 million range and SMG in the 12-24 (maybe even 30+) million range. Mario is harder to estimate because it's harder to guess just how high the Wii's sales will go and what the exact tie rate will be. Halo is easier since the 360's ceiling and Halo's tie in ration is more evident.

Don't think that just because many casuals are buying the Wii for Wii Sports and Fit that they won't ever buy another game. For example I've seen several old ladies in Game Crazy talking about buying a DS to play Brain Age or Cooking Mama and now they're playing NSMB. Similarly my gf plays Wii Sports yes but she saw the Mario trailer online and wants it. Mario Galaxy could really explode to epic sales since it is probably the ultimate and only must-have gateway game for the ubercasuals.

30 million lifetime sales.... these predictions are getting crazy.

 You just made the biggest mistake again of comparing last gen to this gen

 i thought you'd would be wiser than that..

If Wii continue selling like it does now than of course Galaxy will sell more than HALO. I say around 10 million for HALO and 15-20 million for Galaxy. Nintendo wins on the fact that Japan don't care about XBOX or HALO

You must hone in on a few words and ignore the rest of what people say since this isn't the first time I've seen you do so.  I didn't predict anything, I guestimated.  12-24 million are the reasonable ones, and 30+ million was the less reasonable (crazy) everything goes right scenario, hence it was set off by itself in parenthesis.  All I'm saying is SMG has the possibility, however remote, of doing it. Halo 3 does not.  Heck, I dount Halo 3 even has the ability to break SMG's low end estimate much less it's crazy high end estimate.

EDIT:  Either that or you caught the end of the guy above me, he gave 30 million an outside chance also.

Albionus just covered a number of the things I considered with my crazy prediction (see sig). If I might add a few more insights....

1) People know Mario, people grew up with Mario. This by itself will not sell epic numbers of games. But combined with a great deal of excitement spread by word of mouth, I think we will see that Nostalgia of youth and the greatness that was, and could be again. It may well drive people to attempt to recapture some of that magic while giving their kids a chance at a taste of what they had.
2) I see the potential for a fitness fad hitting the Wii as a result of the balance board, and if a fitness fad hits the Wii its number could very easily balloon (no reverse pun intended). When/If that fad were to hit point 1) comes into play big time. Because if you were 10 when SMB came out you are 32 now, and probably have kids (statistically speaking, 2.09 kids [CIA FactBook, 2007 est.] in the U.S.).
3) I believe the Wii is going to have one more surprise for all of us this holiday and it is one I have not heard anyone mention anywhere. What do you think will happen when families gather at X-mas time and the Wii inevitably gets set up and entire extended families get to see this thing in action? Lingyis' signature says "the Wii is an epidemic.", I think this may be more true than we know. I think that come winter sales are going to be just as strong as ever, as people catch the Wii bug and get that "gotta have it" feeling, and I think this phenomenon continues X-mas after X-mas after X-mas. And again point 1) comes into play now as an entirely new generation of families re-discover the joys of Mario all over again.

Now granted, I am well aware that a large part of this is based on speculation, but isn't that what a good prediction is about? Coming up with your theory of how it all ends is one thing, but to back it up with a theory of how it all gets there is quite another thing, and I think ultimately lends to (as a community anyways) the potential for more accuracy in the predictions. If nothing else it leads to more interesting predictions, that I'm sure of.

Edit: I just wanted to add that a lot of folks over the past year have continiously tried to quanitify the Wii by comparing it to the way other "similar" (whatever that means) technologies have performed.  And the one constant is that they always find a surprising outcome.  I really don't think an accurate prediction of Wii sales can be made without at least giving large consideration to the track record of the Wii going outside the confines of the normal sales trends. 

I really see Halo 3 selling 9-12 million in life time sells with the majority coming out from America. Super Mario Galaxy will sell more than 10-16 million since its the true successor to Super Mario 64

Seeing how well these two titles do is going to be extremely interesting.

The userbase of the Xbox 360 is almost entirely composed of active hardcore gamers who like online FPS-type games, and even now the best selling game on the console is something of a Halo-clone, which is constantly compared to Halo 2. Remember, the main criticism (and admitted fault) behind the second Halo was how it was rushed and didn't have the few months of polishing time the original had. The developers have had all the time they'll even need on Halo3, and it looks like it's going to be the absolute pinnacle of its type of gaming, and I believe it's going to have one of the highest attach ratios in the history of video gaming, not counting bundled titles of course. Then again sales of over ten million are far in the future, due to the not all that high and slowly growing userbase of the 360.

Super Mario Galaxy on the other hand is the true successor of Super Mario 64, and hopefully brings back the awesomeness to the series after the slight drop in quality that is Super Mario Sunshine. Nintendo's best developers have had years and years to forge it into a masterpiece worthy of the greatest games of the 90s. It's probably going to beat the best selling Gamecube games on name alone, and has a solid chance of hitting octuple digits if it's as good as we hope, especially if the Wii ends up moving around PS2-level amounts of consoles.

Galaxy will outsell Halo 3. No question on this one. (ok, if the game is generally bad, then it won't. But I think the odds of that are remote.)

I think TheSources original predictions are incredbly generous. I see 10Million for Halo3 (assuming no Halo 4) and 15 million for Galaxy.

It'll be close, but SMG should do well in Japan, and that'll be enough for SMG to beat H3. It's hard to really compared 2 games...One will do rather well overall, and one will do only good in 1 country.

SMG -

2.75m in Japan
5.5m in US/NA
3.75m in Europe
______
11.0m Total


Halo 3 -

125k in Japan
7.825m in US
2.75m in Europe
______
10.75m Total