Most of the core. Most core gamers buy maybe one or two games a year, and they're usually the biggest games of the year. Modern Warfare, Assassin's Creed as such, would be very 'mainstream'. So would Super Smash Bros. and Mario Galaxy. Anything that sells multi-millions could be considered mainstream, really.

Though personally I find it difficult to call almost any gaming 'mainstream', considering how unnaccepted it is compared to TV, movies etc.

I know it's aiming to be a hit in Japan, but I'm skeptical that it will be that big there.

Could u give some examples of mainstream games that didnt necessarily sell 5-10 million. Name some 1-2 mill mainstream games, HD or Nintendo. (since no one believes Metroid M can sell 5 million, I assume)

I don't understand, I'm not being too strict about the definition. There's no particular quality that decides whether something is mainstream or not other than it's reach. You could call any game that sells 2-3 million somewhat mainstream, and something that sells 1-2 million would border on it (likely most of it's buyers would be core but not enthusiasts).

Super Metroid sold over 600k in Japan, the same as Twilight Princess.  

It's too early to call, but I tend to lean towards the Malstrom "big fail" point of view on this game.

It still depends a lot on the actual gameplay. If it turns out to be a 2D game with 3D graphics, it could be a pretty big hit. If it's a 3D action game, depends on how it plays. I don't think the story elements will do a lot for it. People looking for cinematic experiences are focused on the HD systems.

But if that's the case, and knowing that each Metroid Prime sold 1-2 mill (the first Prime even 2.8 mill), then why even ask the question in the OP: "will Metroid Other M be the Metroid to sell to mainstream?"

What is a mainstream/casual gamer exactly, please if you answer me without using "you know" because I don't.

Both seemed to be used as the same, I thought hardcore was mainstream... then it turns out hardcore is now casual or maybe mainstream is now casual....

If that's the case why would everyone claim hardcore games don't sell on wii if hardcore is mainstream and then they say casuals buy things Wii yet now casual is mainstream; but if if they are different things then which is mainstream?!

If they are not then I'm confused. Clarity please!

no i dont think it'll sell to mainstream gamers. i think it'll only sell to metroid/team ninja fans.

i think it'll sell about 1m - 1.5m WW

i also think it wont be a huge hit critically, prob average a 85 on gamerankings/metacritic

Obviously he means will it sell bigger than that. It's a relative term. I would say the other Metroids border on mainstream, but they're not that mainstream. Mainstream wouldn't mean the demographic that buys Call of Duty in particular though, it could sell to completely different people and still be 'mainstream'.