Heh, I would of thought it'd be the opposite complaint. They did too much in so little time. :V From the start we learn Cosmo is the last of her kind, her being the lone survivor part of why she's so timid, unknowingly to herself she had what amounts to a spy camera attached to her that Shadow attacks her about, then it turns out the Metarex are actually some of the male members of her species that went haywire, and she was really close with Tails (That one depends whether you not liked their relationship or not, maybe I was a dumb kid back then or something. But I shipped them a bit. Making things worse for me when Cosmo died :V)
Again though even if it not for Cosmo. There had to be some feeling bad for Tails at the end, even 4Kids didn't really censor the fact Cosmo died.
But I digress, I think that's enough Sonic X talk for me.
Maybe for a bit of a change of subject, I kinda wish the Amiibos had certain effects across multiple games instead of them all being the same as most of the others (Like Hyrule Warriors besides the Zelda related Amiibos you get a random item). Like it would of been awesome if having a Sonic Amiibo gets you the equivalent of a super speed cheat code in other games besides Smash xD