Metroid was never a huge seller... 1 million lifetime to date.

The difference is, Nintendo seems to be trying to do with Metroid what they did with Mario Galaxy and what they're trying to do with Zelda Wii.  In other words, 'reinvent' the series once more.  Metroid Prime was a nice start and did well i nthe west, but truth be told, it was limited by being both on the GameCube and not being exactly 'Metroid' like.  Sure, it had some of the Metroid feel, a lot of the Metroid items/weapons and did a great job utilizing the Metroid style, but in the end, it was exactly what it tried to be, a Metroid 'First Person' game.  This game is looknig to go that next needed step.  To truly bridge the gap from the fast paced, precision and timing based 2D combat of old school Metroid games...and put it in a 3D game.

As long as it truly does that and gets some solid marketing, it may have a chance to even double the sales of Metroid Prime.

between 1.5 and 2 million sales, Although it is early to make a prediction yet hopefully nintendo push this game and prove me wrong.

i'd say 2 million, seems like nintendo would like to push this one...

it won't sell

Don't get me wrong, the game sounds like its going to be amazing but I just don't see it selling 2+ million. If you look at the history of the Wii, most games not related to Mario or fitness/casual games have failed to sell multiple millions. The only exceptions I can think of are Zelda and Smash Bros. Not trolling the Wii at all (Its my favorite console..) but its unlikely to change with this game so late in the cycle.

Well like I said before, most Metroid games sell between 1-1.5 million, mostly due to sales in America.  However, this game has an ace up its sleeve, utilizing the development of Team Ninja, one of Japans favorite niche studios who regularly pulls out about a million in sales from Japan each game based on name recognition alone (Dead or Alive/Ninja Gaiden).  If you couple the possible added Japanese sales this time around plus a possible increase in marketing and 'wow' factor for the series being 'revived', the game could sell a lot better than you think.  Maybe not as well as Mario Galaxy, but more than the standard 1-1.5m each Metroid usually does.  Perhaps around 2-4 million.

Plus you also should look at the fact that its on the Wii, a system with nearly 4x the userbase of the GameCube, and has much more appeal to the core Metroid fanbase as its trying to 'go back to the roots' of Samus and the gameplay of the series.  Both those things could increase its sales over the Prime series.

I'd guess around 2 million, but it could be higher. I recall Reggie saying 2-3 million lifetime was the target for Other M. If Prime 1 could exceed 2 million on the Cube, I think there is every chance Other M will hit 2 million or more.

Well, I hope you're right. We shall see..

2 Million is my guess.