Heretic
Even if two Pittsburgh teams are in the top 10, in the grand scheme of things, I look at this list as flawed due to the way it seems more like a list of the most popular teams overall currently and not an actual "best fans" list. As people have said, the presence of the Cavs and not the Browns on the list is a huge flaw. No matter how much they lose, the Browns sell and have the most rabid fanbase of any of the city's three teams. The Cavs were HUGE with LeBron, but before him, they were the worst (or close to, depending on the year) team in the NBA in attendance.
You could put the Penguins in that boat. With Crosby, Malkin and a recent Stanley Cup, they're the hot shit in the NHL. But it wasn't that long ago that it looked very possible they'd be relocated because they sucked and weren't drawing.
If you're talking about the true "best sports fans", it's silly to pick one particular year and say, "because everyone's buying this guy's merchandise and the team's selling out nightly because they're a title contender, they have to be elite!" if it's a known fact those fans aren't going to be rabid if the team has a couple down years.
"Best fans" isn't a year-to-year thing...it's a long-term thing. When I look at this list, I see some teams whose fans will support them through thick and thin...and I see teams whose fans have been noticeably absent when the team sucks.