Post your ideas about songs that you'd want to hear covered by certain singers (even if it's impossible because they're dead). You can give a reason why: You think it would suit their voice or it'd be interesting/funny.
To kick things off:
Freddie Mercury - Maria from West Side Story: It'd be great to hear him sing the sustained B♭4 in the middle and bring the emotional intensity the song requires.
Brian May - Old Man by Neil Young and Bridge Over Troubled Water by Simon and Garfunkel: He's good at singing the more thoughtful songs (and I just want to hear him sing them to be honest).
Jim Morrison - Basically anything by Frank Sinatra.
Vitas - Phantom of the Opera (both duet parts. Alternatively, Aleksandr Gradsky as Erik, with Vitas as Christine.) Happy Rhodes - Take On Me, because she's one of the very few female singers who actually could sing it as it's written, with the sustained A2s (as well as the sustained E5s) and I think it might sound cool.
Steven Tyler doing Prince's "Endorphinmachine." Jeff Buckley doing Sinatra's arrangement of "I See Your Face Before Me." Sinatra and Antonio Carlos Jobim doing a low key bossa nova version of David Bowie's "Stay."