What's interesting though is that people who played Metroid Fusion first probably don't jive with earlier games in the series for the exact same reason that veterans don't like Fusion.
Fusion is constantly rewarding you, and this is evident, for example, in the constant returning to ADAM. That pick-up-and-play system that provides little doses of accomplishment throughout the game is completely at odds with the self-sufficient goal setting of the earlier titles. So the appeal of Fusion, where you receive a goal, act it out, and report back is actually at odds with what made the initial games appealing in the first place.
In Super Metroid and the like, the fulfillment of your curiosity is assumed to be reward enough for progression. It works, as well - I love Super Metroid! It creates an environment that is exciting to slowly uncover on your own. So as a player you rely totally on yourself to make decisions.
What's interesting is that in a way, Metroid Fusion isn't a Metroidvania at all! I can see why veterans felt ADAM almost insulting, because the play environment they came from fostered a completely different relationship with the player. Super Metroid sets the player up to feel satisfied with themselves and their own ability to solve problems, whereas Fusion has the player actively seeking gratification from an outside source (ie, ADAM).
When you look at this dichotomy, it's actually pretty evident why the Metroid franchise is a less viable enterprise for Nintendo to invest in. We live in a time where people get addicted to Candy Crush - and that's because it's constantly telling you you've done a great job. What people tend to enjoy about Metroid is that sense that you are alone, which does require you to think on your toes. This necessitates an active engagement from the player. I think to more and more people (and perhaps this is a subconscious shift) that seems like work. Look at the thread I created recently about backlogs! People's attitudes to their purchases are often begrudging, like their backlogs are looming tasks that need to be worked through.
It's interesting - I think that actual act of purchasing a game is enough of a gratifying rush for some people. Playing the game is... I don't want to say it's an afterthought, but - it's just fascinating; this system that's playing out in society at the moment. We had a thread in the OT recently about how pornography and video games are creating a masculinity crisis in young males - but I don't think it's the things in themselves but rather the parts of them that reward viewers/players constantly, ie "HEADSHOT" or "Mm yeah, your dick is so big"
Haha. Strange world, huh?