I can't really say I have a favorite... I rotate around among different receivers, because I like the sound of each of them, even though they are different.
I have more Marantz than anything else, including both the 2265 and the 3385B mentioned by others, but that is as much a function of buying opportunities and early exposure than anything else... the two mentioned, and other Marantz receivers, have a wonderfully rich yet detailed sound. The "three Martini" label sort of fits. BUT they MUST be recapped to sound right... as-is Marantz receivers usually are a bit disappointing until they get "worked over".
I have five large Pioneer receivers, and they are wonderful, too. A bit more "analytical" and less "lush" than the Marantz, but still wonderful to listen to. The newest is the 1010, which gives an excellent first impression, but it is "as found" (not cleaned up or recapped yet), and I haven't really had a chance to listen to it yet.
I can understand what was said about the Sansui sound, but I don't find it at all "un-inviting". I have a 9090, and I think it is very nice, and while I don't have a big G-series yet, I've heard them and think they are great, too. The midrange in particular DOES "invite" me to listen, and I find their sound quite satisfying. [I know this discussion is about receivers, but some of the Sansui separates do NOT have weak highs, IMO. I LIKE Sansui amplifiers!]
My Sony STR-V6 certainly deserves a mention: it has a very nice sound, too. I think they are seldom mentioned, just because they are relatively uncommon. That doesn't mean they don't sound good!
So do the Harmon Kardons.
So do the Luxmans. In fact, I'm surprised no one has mentioned Luxman yet. Perhaps that is because, like the Sony "V" models, they are not very common...but the luxman has a rich, lush-yet-detailed sound that reminds me of the Marantz sound. I like it VERY much.
I don't have any MCS or Concept or even Yamaha receivers, but the sound of the Yamaha B2 amp is a pure delight: as was said, it is about the closest thing to "pure wire with gain". If the receivers sound anything like that amp, I should like them, too. I don't have any Kenwood receivers, but had Kenwood gear back in college and thought it was excellent back then. I don't have a Mac receiver, either, but have heard them. Excellent sound quality. I wish I DID have one! Not sure about Technics or other brands; just haven't heard them enough to judge.
My newest receiver is the (TOTL in its day) JVC JR-S501. I haven't had a chance yet to really listen to it, but I'm expecting good things, based on what other owners have said online. It's a very prized receiver among Germans in particular, it seems.
Not to be a spoil-sport, but I really do enjoy ALL the different receivers. Some particular songs will sound better through one than through another, but then a different song will sound best through a different receiver. Sometimes I'm more in the mood for one type of sound than another, and will gravitate towards one receiver. On another day, I'll want to hear a different one. And speaker (or headphone) choice also makes a difference: some synergistic combinations are "made in heaven" and other combinations are not.
And when I want REALLY good sound, just the best? One word: Separates. The really good separates, of course.
