I think you're all putting words into Starcraft's mouth.
"This game will be awesome for people who like this genre" I think he meant the same thing everyone means--obviously you have to like a genre in order to like the games in that genre. But if you do, this game will be awesome, which isn't true about every game in any genre.
"Stealth is becoming bit of a niche" -- not "MGS4 is niche" but the genre has become a niche- he was talking genre, not game. Obviously shooters are less niche than stealth games. Is that realy up for argument? Yes, MGS games transcend it somewhat, but as a good friend, and huge PS and MS fan, said to me last night "MGS is about as nice a franchise can be for one that sells as well as it did. Lets look at sales:
MGS: 5.59m sales on an install base of 100m
MGS2: 5.56m sales on an install base of 120m
MGS3: 3.97m sales on an install base of 120m
GTAIII: 11.6m sales on an install base of 120m
GTA:VC: 14.2m sales on an install base of 120m
GTA:SA: 17.1m sales on an install base of 120m
GTAIV: 8.1m sales (so far) on an install base of 31.7m (so far)
Halo: 6.43m sales on an install base of 24m
Halo 2: 8.46m sales on an install base of 24m
Halo 3: 7.82m sales (so far) on an install base of 19m (so far)
(yes, I know I'm leaving off Substance and Subsistence. Neither would have made a ton of difference with inclusion).
MGS games simply do not have the mainstream appeal of most games of similar quality. Of all the "huge" franchises in video games, they consistently sell near the worst with near the lowest attach rate. You can see the same things if you compared MGS to Mario games, Zelda games, Smash Brothers games, Mario Kart games, Pokemon games, Gran Turismo games or Final Fantasy games (though PS2 FF games actually are pretty similar in sales to MGS games, if still all better sellers than MGS3) This is not a knock on the games by any mean. They're phenomenal games, which is why they've been able to transcend their genre to the extent that they have. But stealth is a niche genre. Always will be.
Granted, MGS4 might be different, since it's by all account a stealth/shooter hybrid, but we'll see when it comes out.
EDIT: Or maybe Starcraft will jsut dig himself into a deeper whole. I still stand by my point.
Atari 7800 (Sold), Intellivision (Thrown out), Gameboy (Lost), Super Nintendo (Stolen), Super Nintendo (2nd copy) (Thrown out by mother), Nintendo 64 (Still own), Super Nintendo (3rd copy) (Still own), Wii (Sold)
A more detailed history appears on my profile.