Just to clarify, you are talking about cruising houseboats built from the mid 60s to present. The very best is a Pluckebaum, that was an easy question.
Of the ones mentioned in your title it depends on the condition of the boat at this point in time. With the exception of Gibson and Holiday Mansion production has ceased some time ago on these brands. Some that you didn't mention in fiberglass include BurnsCraft, HarborMaster, Bluewater, WhitCraft and others. These brands were considered as the next rank up. Aluminum models from Marinette, and KingsCraft were considered a step up also. Steel boats from RiverQueen and SeaGoing were plentiful but are becoming extinct.
All boat manufacturers used basically the same mechanical components and stoves, heads, fridges, etc.
If your looking at an older boat, condition is paramount, brand is secondary. I would recommend you look for boats having MerCruiser or Volvo automotive marinized drive components for the simple reason parts and service expertise is available no matter how old the unit. The only exception to this would be "Merctrans" equipped units which are problematic. Dana and OMC equipment have significantly less service availability.
Edited: 01/17/2009 at 04:10:32 PM by OLD HOUSEBOATER
Interesting comparison, most would be Chevys, KingsCraft would be a Pontiac, BurnsCraft would be a Buick, Bluewater would be a Caddy as well as most WhitCrafts. Pluckebaum would be at least a Bentley. What say you??