I think that a non-profit insurance company is your best bet.  The best one I had was actually a trust, not really an insurance company.  It was established for public employees of the county I was working in.  You need someone who’s not going to try to make a profit off you.

It is impossible to rank various types of health insurance from a general perspective for a few reasons.  First, we would need to agree on what is "best."  From whose perspective are we judging what is best, the market, the consumer, society? Second,  do we mean best from a monetary point of view, from a preventative medicine point of view, from a "choice" point of view?   Third, no matter whose perspective we are viewing this issue from, all of these types of insurers offer choices from a menu that varies in premium, deductible, hospital and doctor choices, and co-pays, and all have "gate-keepers" built in, so that various kinds of coverage must be approved (or are disapproved.)  Fourth, there is often a kind of geographical variable, depending on what kinds of choices are available within one's community, with many rural areas having few medical facilities and doctors and many urban areas offering a wide range of choice.  With the new federal health care statute, there have been and will be some changes in all of this, but the basic premise remains largely the same, that what is best depends on many variables, and there are entire books written on this very issue.  The fact that this question has no easy answer is one factor that has made this such a difficult issue politically, with various factions being able to argue that their ideas are "best" for very different reasons and from entirely different perspectives. 

From my own perspective as a consumer who must purchase her own medical insurance and who lives in an area with many hospitals and doctors, all quite competent, my preference is an HMO that has everyone who takes care of me within the same "loop," keeping my co-pays and premiums lower than if I had many choices.  In an ideal world, for me, we would have universal coverage for everyone, which would reduce the costs and which would prevent people from dying because they have no coverage, which does happen now.