At the very top, the Zeiss Ikoflex and Minolta Autocords. Next, the best Yashicas, and the MPP Microflex - these are very close to the above group. Next, most of the rest of the Yashicas, and the Ricohs and MPP Microcord and Rolleicord. Next, lots of others next, the Seagull. Last of all, the Lubitels.
I've left out the Mamiyas, which are excellent tools but rather different to the rest, and obviously the Rolleiflexes. In truth any of them from Seagull upwards are capable of good results - the best have somewhat better lenses and are easier to use and better-made.