Are any really better than the others - Marantz, Yamaha, Arcam, NAD, Rotel, et al in sound quality?
Yes, they are different than others. When you look at a receiver you group them together in price ranges. Next you look at features such as how many channels, the power rating, what type of room correction, are they networked, etc.
After that it boils down to preference. Marantz and Denon are both made by Masimo, but they sound different. Yamaha has a feature called Auro- 3D but Anthem doesn’t. Onkyo offers Dirac room correction but Anthem has ARC. I got a GREAT deal on a 9 channel Onkyo receiver because it didn’t have something called IMAX Enhanced and the model replacing it did. That feature wasn’t important so I bought it at around a 70% discount brand new. So I can only tell you my favorites, but "best" is what is best for you. My top 3 favorites are Marantz, Onkyo and Sony. They all have nice reviews on youtube.
EISA recently presented their annual awards and they test gear, check out: