i sad MAIN franchise , that includes -Mario, -Zelda, -Pokémon,-Metroid,Smah Brothers and alike, games like F-ZERO, Star Fox and Animal Crossing for me all of those are in the second line-up of franchise at nintendo.

Star Fox assault is a Nanco game far as i know about it , sure nintendo should sad something like "Keep it on air" but still was not a direct nintendo developed game , and wait o know what you will say now "But other M is a tean ninja game" no its not its a "Nintendo collaboration with Tean Ninja" and Sakamoto itself in directing the all thing so rest sure the game will rocks... 

Thought you might try to pull this, but no dice. If you can somehow explain to me with any single reason why Metroid should be counted more main than Star Fox, then go right ahead - but the sales suggest otherwise. Nintendo's main series are Mario, Zelda, Pokémon. People just want Metroid to be part of the trifecta when in fact... Well, it's not.

Star fox one day was in the first line-up during the SNES and N64 eras but after that no more, just count how many Star Foxs games was released in the last decade that where consider to be a AAA title only one Adventures , in the other hand Metroid had 4 AAA games being all the 3 prime games on the cube and hunter on the DS, and Metroid even got a Spin-off on DS. need any more evidence of why metroid is in the first line up, and Star fox is not ? And if you are talking about sales , well i havent check on it but i pretty sure that the Metroid series has out-sold the Star For franchise, and Nintendo would never let a third-party handle the development of a Metroid game like they did with Star fox giving it to Nanco.

They're letting a third party handle Other M......

^^ which is a misrepresentation on both your parts. Assault was as much "3rd party developed" as Other M is. There was an SPD group working there just like there is one here, just as there is always an SPD group working when a Nintendo franchise is being farmed to a 3rd party developer.

FAIL ...

The game is presented by "Project M" that is a join venture kind of collaboration with Tean Ninja, and directed by Sakamoto the same guy that has being working on every single metroid game ever released with the exception on Prime Hunters and Metroid Pimball.

Which is the identical situation as in the other cases.... Or do you think it makes it more special that they called it "Project M"?

This half true in my opinion sure that always is a group of nintendo people on everything that is related to any nintendo IP, but Other M is in a all new level of collaboration, for instance the producer for Star Fox 64 was miyamoto , i wont lie i dont remember if he was the producer of assault but i sure that Sakamoto was the director on every single metroid and still the director on Other M. and one last thing to note assault never has was consider a AAA title.

http://pt.wikipedia.org/wiki/Star_Fox_Assault

Please check the Link it says developer : Nanco Publisher : Nintendo

http://pt.wikipedia.org/wiki/Metroid_Other_M

Now check this one it says developer : Project M
(Nintendo SPD Production Group 1, Team Ninja, D-Rockets) Publisher : Nintendo

Sorry the links may open for you in portuguese (i from brazil so the wiki pages open in portuguese for me) Any how you can see the difference here... the SPD1 is directly working on the project.

Thing is, critical reception really has no place here. We're talking about Nintendo's most notable series, and Star Fox 64 has sold more than any Metroid-game ever did by more than a million. Basically, Metroid is one of Nintendo's main franchises here simply because you want it to be.