I am fairly new here but even I had no trouble guessing who the votes for Brian May and Roger Taylor were coming from. Queen is far from my n. 1 band but you have to give it to them - apart from having the greatest rock singer ever, they also had the other really good vocalist. If we were to rank bands based on their average vocal competence across all members, Queen would be easy winners...
I had a list of 40 or so, with Sinatra, Collins, Bono, Steven Tyler etc, but, as others pointed out, this was a ‘favorites list’. Brian and Roger LVs added to my enjoyment of Queen LPs FIVE decades ago. I sorely missed that after ‘The Game’, and it's probably why 'Let Me Live' is one of my ten favorites, because they are ALL featured.
Those two did provide me enough on their own releases to give me three really good and very often listened to ‘best ofs’.
Off the top of my head regarding multiple lead vocalists:
The Beatles had Paul, John, and George (yeah, there was Ringo, too).
Styx with DeYoung, Shaw, and Young (I really enjoy JY's ‘Midnight Ride’, ‘Miss America’, ‘Great White Hope’, and ‘Snowblind’)
Chicago with Robert Lamm, Peter Cetera and Terry Kath.
Supertramp with Roger Hodson and Rick Davies.
Journey hit the big time with Steve Perry, but the duets with Greg Rollie on ‘Feeling That Way’ / ‘Anytime’ and ‘Just The Same Way’ took the songs to another level (how petty of the band not include those songs on their ‘Greatest Hits’ to keep Rollie from receiving additional royalties! It’s not their ‘Greatest Hits’ without those tunes
).
The Eagles: Frey, Henley, and Meisner and Leadon. Oh, and then there was Walsh and Schmidt
Fleetwood Mac with Buckingham, Nicks, McVie
KISS Stanley, Simmons, (Criss and Frehley to an extent)
REM Mike Miles had some good offerings with ‘Texarkana’ and ‘Love Is All Around’
A shame DeGarmo wasn’t used for changes of pace with Queensryche. I really enjoy ‘All I Want’. Variety can be a benefit.