Metroid's a bit of a hard sell. The first game was pretty unique for its time, but also insanely obtuse. If you didn't basically shoot, blow up, and Screw Attack everything you saw, animate or inanimate, you never got anywhere. The Game Boy one wasn't much clearer. Super Metroid was marginally easier to follow (and masterly atmospheric), but it was still too obtuse for more impatient gamers. The Prime games have done a lot for the series in terms of making goals clearer (though you still end up wandering aimlessly or lost a lot of the time), but there are a lot of first-person shooters out there to compete with them.
As for Fusion and Zero Mission, well... Most complain that Fusion is too story-intensive, which is is, and Zero Mission strikes the better balance of the two. Had it actually been advertised a bit, it might have managed to sell better. At this point, the best thing for the series would be another 2D entry which does a better job of making clear how to move forward. Not an easy task when your environment is futuristic, but it can be done.
Sky Render - Sanity is for the weak.
