This is a ranking strictly based on room quality & hotel amenities. The casinos are another story for another day:
1. Fremont - nothing special, but nothing to complain about either (the women around me might disagree about the smallish bathroom, but that's generally true downtown)
2. El Cortez (Tower) - Has seen better days, but large, quiet, and decently appointed
3. Four Queens - North Tower is closer to the action, but noisier and the rooms are more threadbare
4. Golden Gate - A mix of old and new; YMMV with ongoing renovations
5. Las Vegas Club (South Tower) - On my last visit, the room itself wasn't bad, but lots of little things added up to a subpar experience
The other places I have not stayed, so I can't comment.