Agreed. We should really stop acting like Metroid was ever in a comparable situation to Golden Sun. Metroid is a long-running Nintendo series that has been around since the NES. It hasn't seen an entry on every single system that Nintendo has released, but it is still relatively a staple. I doubt Nintendo will ever give up so easily on Metroid.
Federation Forces was a spin-off, and I sincerely doubt that Nintendo would have abandoned the series because that title didn't sell so well. It's like saying that Animal Crossing Amiibo Festival not having sold well means that the Animal Crossing series is in a questionable position. Hint: It's not.
Golden Sun has seen no spin-offs, so its last title was a mainline Golden Sun game. Golden Sun does not have the legacy of Metroid, as it's only been running since the GBA. With the last mainline title not selling so well, Golden Sun *is* in questionable territory.
I keep hoping we'll see some attempt at bringing it back. A 3DS remake of the original could have been something they could have revealed at this E3. It would have been prime time - the 3DS is in that stage where it has sold very well and a lot of people have one. But sadly that didn't occur. I don't know if there's much hope anymore.
Metroid Prime is the best selling game in the franchise, just beating out the original
Metroid at about 2.75 million copies, while
Fusion racked in about 1.6 million.
Prime 2 got less than half as many sales as its predecessor.
Prime 3 hit about 1.6 million.
Zero Mission, regarded by some fans as "the best 2D
Metroid ever", and the game that provided the engine for the "smash hit"
AM2R, only hit 0.8 million.
Hunters dropped even lower, down to 0.7 million.
Other M was actually a resurgence for the series overall, but still a massive drop for 3D titles, down to 1.1 million. And then came
Federation Force. 0.1 million copies, the worst seller in the series, even lower than
Prime Pinball.
For all the praise, all the attention that this series got, it doesn't sell that well, historically. And the recent games have been in a constant decline that can quite fairly be called a "death spiral".
You're right,
Golden Sun doesn't have
Metroid's duration. 1.76, 1.22, and .79 million for each game.
Metroid comes back after a hiatus of 7 years following a game that sold 1.1 million (
Other M), and hits a total of 0.1 million with its next game (
Federation Force).
Golden Sun comes back after a hiatus of 8 years following a game that sold 1.22 million (
Lost Age), and hits a total of 0.79 million with its next game (
Dark Dawn).
Metroid has a longer series history, especially on home consoles, and lacks some of Metroid's visibility because of that. But it also has lower overall development costs (especially compared to the highest sellers in the Metroid franchise), and better sales history when looking at the recent games.