Galaxy 2 yes because Mario is recognizable to the Blue Ocean crowd and there's plenty more where they all came from which is why Galaxy and NSMBW already being out won't matter, Metroid not so much as it's always been a really complex concept and game for many to get into.
But the 'blue ocean crowd' did not buy Galaxy-- so why would they buy Galaxy 2? Just because it is a Mario game does not mean that people will buy the game on mass. If people bought games just because of Mario, then Super Paper Mario, Mario Tennis, Galaxy, Sunshine, Mario & Luigi, etc. would all have sold about 20 million.
I'm not sure I agree with the idea that Metroid is to complex for some to get into. Metroid is more of a niche series (I feel odd saying niche about a series that routinly sells over a million a game, but this is Nintendo we are talking about) and has never been a big seller. I wouldn't describe the metroid games as complex-- you shoot things and get power ups to access new areas. My wife 'gets' the Metroid games, but she still doesn't like them.