Heroes ended with every element it needed, including the next horizon...
With or without Issac, the future will always be on our line of sight.
Issac Mendez - painted the future
Ted Sprague - released radiation
Karen Sprague - Ted's wife, heart of gold
Eden McCain - voice activated mind-control
Chandra Suresh - Mohinder's father, had a great kid
Charlie Andrews - photographic memory
Every Hero murdered by Sylar - metal liquification, super-hearing, telekinesis, etc.