what Sylar does with the brains
Probably the thing I most wish they would've answered.
shareI would've liked that too, but that would mean the writers of Heroes actually had a long term plan, and we know that wasn't the case. Heck they couldn't even decide what is Sylar's original power. Instead the fans were left wondering what should've been basic questions and answers about Sylar, and some of those question wouldn't even be answered until season 3.
That scene in season 3 when Claire ask Sylar if he's going to eat her brain really says it all. The fans put way more thought into their fan theories than the writers do with their story, and the writers even reference and later use the fan theories instead of the other way around? That's like a new level of lazy writing.