It's hard to rank them. It's like rating cars and tennis shoes. Every mfg makes cheap ones, better ones, and a good quality model. Just because you buy a Nike or New Balance shoe doesn't mean you're getting a good shoe since they make models from $40 to $200, maybe more.
Generally I dislike the statement that the more you pay, the more you get because some businesses just plain over charge. But in a MH, if you pay at the low end, you're generally going to get a lesser product - but I'm not saying you have to go buy on the high end either.
Most build both gasser and diesel models - what do you want. You're going to pay more for the DP, but in general, you're going to get a better, more solid built unit.
Decide on a gas or diesel, length, number of slides and find a general floor plan, then you can start looking at brands without getting too side tracked. Don't forget to figure out what you want to spend before you too carried away looking.
We bought a 2005 Fleetwood Excursion 39S three years ago and are very happy with it. The Excursion is just an upgraded version of the Discovery in those years.
Bill