In retrospect, given how little respect this show receives, part of me thinks it should never have been attempted. At least not as a weekly series.
Audiences are too used to superheroes being people in tights who run around saving the world every week and cracking wisecracks. And god help us if any of them have any personal problems outside of fighting crime.
Heroes was a good concept that should have been restricted to a movie or a mini-series. Aside from the difficulty of maintaining an arc-heavy series in an anti-arc environment, they should have known that the demographic they were aiming for has, on the whole, certain demands on superhero series that the concept of Heroes itself could not hope to achieve, without violating its own internal logic.
Put another way. Back near the end of Season 1, Clare Bennet makes a joking remark about whether she should get herself a superhero costume. I think the show would probably have been maintained its popularity if she and the others had done just that.
Alex
Ah, the old "viewers didn't get what they wanted, so they knock the show" canard.

It wasn't necessary for them to put on uniforms and start fighting aliens. It was necessary, however, for them to eventually realize that they weren't ordinary people, and they needed to deal with that fact instead of trying to hide it all the time. Instead of constantly going their separate ways, band together and figure out how they could protect themselves and each other. Use their powers responsibly.
Basically, they would have been best served by forming a more benevolent version of the Company as soon as they realized there's a reasonable number of superpowered individuals out there. The Company was one of the more interesting concepts this show ever put forth, and yet they spent the first three volumes dismantling it. There should have been consequences for that--who is out there stopping the bad SPBs now?--but, like everything else, they just sweep it under the rug so Claire can whine about being abnormal and Hiro can continue to act like a child.
There is no progression in these characters, and nothing interesting happens to them, so what's the point?
I'll watch this show until it's over, just so I can see where things end up, but they absolutely gutted the potential of the series. It was almost like they had a checklist of things the audience would find interesting, and quickly struck them all out.
No one seriously expected these people to become X-Men or anything. This show is pretty much grounded in the real world. But we're four seasons in at this point, and it's about time they figured out what the audience realized long ago: they aren't regular people and they can't ignore their abilities, or those who would use them for evil.