For me, there isn't much reason to rank promotions outside of the UFC. I view most fighters as on their way out of the UFC, trying to get in the UFC, or just regional level fighters who are content to stay at that level. I hate to generalize, and that is probably one of the worst generalizations I have ever made. But, that's how I look at it.
The furthest I would rank promotions is the top three, and in my opinion they are:
I have a hard time deciding who is number two, Bellator or Strikeforce. Before the Zuffa purchase of SF, I probably would have said Bellator hands down. But this year, and even before, Bellator has probably had the worst referees and judges I have ever seen. I have seen more than my share of terrible, highway robbery, grand theft, prison ass rape decisions.
In the past however, Strikeforce has been guilty of almost-as-criminal mismatching. Robbie Lawler vs. Matt Lindland? Are you kidding me? Who didn't get 11 points for that first round KO?
That is just my personal feeling on the whole deal. Of course, I love MMA in all forms. I watch MFC, Dream, anything on HDNet, Shark Fights, whatever it may be, whoever is in the cage. There is nothing like an MMA bout.