LOST was interesting and I can actually follow their "resolution", but they did stretch things out too long, throwing out wierdness after wierdness after wierdness and then writing themselves into a corner where they couldn't resolve things any better than they did. It's an example of why even with JJ at the helm, the guys running the networks should ensure that shows have a clear script/pattern to follow when they get extended.
Heroes I blame more than LOST for blowing chips actually, since that show should never have been greenlit. Their entire problem seemed to be not having the budget to do a super hero show, so they had to find continually obtuse ways of not having any kinds of decent super hero fights, or having people use their powers at all unless they were very easy to do on camera (like telekinesis which can be done with wires and camera tricks.
Lost at least had the budget for what it was setting out to do, and it had it's black smoke monster, wierd sets, and other things in exactly the right proportions. It's failure was in it's writing, but you can at least see why it got approved.
I agree Lost jumped the shark more, because it had everything it needed to be good and stay that way, heroes on the other hand was doomed right from the beginning.