The Bleacher Report has this slideshow where they rank the best fans in MLB. The Astros ranked 21st, or, 10th-worst.
Astros fans swing like a pendulum. When the Astros are hot, the fans are there. When the Astros slip, the fans can't get out of the Big Juice Box quick enough. They've got a very unique ballpark and a recent history of winning, but fans just don't seem committed enough.
I'll open this up to comments. Because those would be fun to read.
The five best?
Cardinals, Giants, Yankees, Phillies, and Cubs.