Meh. The main reason why Houston doesn't have a large amount of loyal or passionate fans is because everyone is split among three sports. Look at OKC, their only professional team is basketball... they draw crowds every night good or bad. Not only is Houston/Texas split between various major league teams, we are also in a region notorious for loving football. Basketball is not first wheel for many here.
That can explain why Portland has passionate fans - only one major team. But I think the thing Houston suffers from is that it is still a young sports city. People who are diehard Cubs fans or Redsox fans grew up watching the games with their granddads who were also diehard fans. Today's Rockets fans in hear will breed the loyal fans in 20 or 30 years, quite literally. I guess it just takes a generation or two.
I have been to a lot of games and other than the lakers, heat, and clippers it was kind of dead. Even the astros with twice as many game draw way better than the rockets.
THIS. The true Rockets fans are a passionate, obsessive bunch. But they are few and far between in a diverse, fair-weather city of sports fans. We are a lot closer to Miami's fans than those of the Knicks, Celtics, Sixers, et cetera.