A lot of people tend to say the Beatles. The Beatles were it, they were cool, they had a lot - but they weren't harmonious at all. In an interview, McCartney once said that their songs were sometimes sped up to 6 times so they could do a lot during one show. The people were screaming so loud that sometimes one Beatles could not hear where the other was during the song... Anyhow, back to topic - I loved the harmony of Aha. But, guess I'm biased because they simply where my fave group of the eighties! Know of the song "Here I Stand And Face The Rain"? It's my fave!
Just about anything from The Zombies' Odessey & Oracle I find to be impressive. Also, some of The Who's early work had some great harmonies.
Funny story about this song...About a month ago I was up at alpine valley for a BMB show. We got a little bored while waiting for the encore. One of my freinds started singing bohemian rhapsody and another friend and I joined in. We sang the entire song. Some of the people around us joined in too. When we finished we had about 500 people around us applauding.