This might be a little macabre, but think about it:
If you had the power both to travel back in time and the power to decide who lives and dies, would Freddy Mercury have survived and David Bowie gone on to the great spaceship in the sky? Or, would things have stayed the same?
The thing is, David Bowie is cool and all... Yeah, he's a style icon... But have you ever actually listened to his music? I tried - I did, but I cannot transport myself to a time and place where Bowie's music is good. But, Freddy Mercury just plain-out rocked. Queen was awesome. Queen is awesome. I know he would have continued to rock had he not died. That gets in the way of genius.
This question has been bumping around in my head for a while. I didn't just randomly hear Under Pressure or anything - I hear it all the time. It's a miracle of rock! Go listen to it right now. Go listen to it, and then ponder who you wish was alive - Freddy or Bowie.