Galaxy 1 and 2 were made by two different teams with two different directors inside Tokyo studio. Galaxy 2 team then made 3D Land.
NSMB series is being made by EAD 4 and NSMB2 was made by interns of that studio basically.
I can't wait when they will reveal what has Galaxy 1 team, EAD Tokyo 1, has been doing all this years!
Galaxy 1, 2 and 3D Land were all made by the same team. All 3 games contain most of the same staff including the most important members, directors and level designers. The only differences are some got promoted to higher positions with each game but they're still all part of the same team.
http://www.mobygames.com/game/wii/super-mario-galaxy/creditsProducers - Shigeru Miyamoto, Takao Shimizu
Director & Game Design - Yoshiaki Koizumi
Level Design Director - Koichi Hayashida
Level Design - Futoshi Shirai, Daisuke Tsujimura, Haruka Kakinuma, Ryutaro Kanno, Toshihiro Kawabata
http://www.mobygames.com/game/wii/super-mario-galaxy-2/creditsProducers - Yoshiaki Koizumi, Takashi Tezuka
Director - Koichi Hayashida
Planning - Daisuke Tsujimura, Futoshi Shirai, Haruka Kakinuma, Shinya Hiratake, Daisuke Sato
http://www.mobygames.com/game/3ds/super-mario-3d-land/creditsProducer - Yoshiaki Koizumi
Director - Koichi Hayashida
Planning Director - Daisuke Tsujimura
Level Design - Futoshi Shirai, Haruka Kakinuma, Hiroaki Hishinuma, Shinya Hiratake, Yuichi Iwasa
What happened was Tokyo EAD used to be one team but then after the first Mario Galaxy, Nintendo decided to split it into two. The majority of the team including all the key Mario members became Tokyo EAD 2 with Yoshiaki Koizumi being promoted to a producer in charge of the new team. This is why Wikipedia list the first Galaxy as a Tokyo EAD 1 game because when it was made by the one team, Takao Shimizu, was the producer in charge of the entire studio.
After the split he was still in charge of Tokyo EAD 1, which is why whoever wrote the Wikipedia page list Galaxy 1 as one of his studio's games, even though all the key people who made it moved to Tokyo EAD 2. Only a small group of people are left at Tokyo EAD 1 which is why they're only a support studio that helps co-produce games with other studio's like Grezzo for the 3DS Zelda ports or makes DSiWare games like Jibun de Tsukuru Nintendo DS Guide.
So Tokyo EAD 1 is probably helping Grezzo with the next 3DS Zelda while Tokyo EAD 2 is making the next 3D Mario for the Wii U.