Was Queen a sellout?

No clue...call Brian May and ask him

Seriously, the same could be said for Genesis, Yes (90125, Big Generator).
I have no problem with bands doing this, commercial success = money!! And they deserve to make a lot of money, especially back in those days only album sales and touring paid the bills.

I think Queen did exactly what they wanted to do.  They could be influenced by changing times and changing music scenes as other bands could, but ultimately, I don't consider that they sold out at all.  In fact, considering that Queen and bands like them make music professionally, I think saying they sold out is silly.  Bands are trying to make a living on the music they make.  So if their music doesn't sell, they are going to have to change their sound so that it does sell or they can go broke and eat grass or change professions.  But again, I think Queen did what they wanted to and they did it well enough that they sold massive amounts of records.  

They are a bit like Genesis, I'm not a big fan of their post-80's stuff but they managed to stay up there.

Of course they sold out. Just compare A Night at the Opera to Works. They made their mark as musicians and the decided to cash in. They were still good musicians, but once they tasted the sweet, sweet wine of success they never turned back. In fact, I believe they even tested their fan base to see what they could get away with. Exhibit One: Flash Gordon Official Soundtrack. Still, they put out some good songs and given their concert performances, I do not fault them, even if I lost interest in them by Jazz. And we are still feeling the loss of Freddie Mercury.

What is musical integrity?

They just changed with the times, and managed to stay popular. Good for them. Even their 80s stuff is still pretty complex a lot of the time, but in different ways. Finding interesting ways to use technology that's available. Some of it sounds corny now, but I could say the same for some of their early songs.

If you listen to their early material (The May/Taylor band Smile, or Larry Lurex) they had their beginnings as sort of a heavy pop band, they were not particularly prog, although they certainly incorporated some of that into their sound while that sound was popular.  They were never a prog band.  Bands have a right to do what they want to do, whether they do what they want due to a desire for popularity and the money that comes with it, or because that is where their musical interests take them.  I think it's wrong to accuse bands of selling out when that is what they do for a living.  We may not like the direction a particular band takes at a particular time, but the band doesn't owe it to us to make sure we are personally satisfied with their product.  

Possibly it also influenced that Freddy got seduced by the role of superstar frontman live and was not interested in playing the piano live anymore, and they never wanted to take a full-time keyboardist, so their format live was limited to a trio guitar / bass / drums (although they had support by a keyboardist and pre-recorded stuff occasionally), so they could not make very complex music which they could not play live.

Catcher10 wrote: No clue...call Brian May and ask him Seriously, the same could be said for Genesis, Yes (90125, Big Generator). I have no problem with bands doing this, commercial success = money!! And they deserve to make a lot of money, especially back in those days only album sales and touring paid the bills.

Aussie-Byrd-Brother wrote: ... I remember some quote from Freddie who described their music as `disposable', in that, it comes on the radio, you listen to it, enjoy it, then discard it and move on after it's finished. I can definitely see that in regards to the direction they eventually moved in, but writing pretty much perfect pop/rock music with cool playing and incredible vocals/melodies is nothing to look down on! Still those early albums are the jewels though!