I also prefer Cohen to Mercury (thought I wouldn't call him a bad singer), but I also think that Mercury is a technically better singer. Of course, they're so stylistically different it's tough to compare. But the important thing here is to distinguish between quality and taste. You can recognize the quality in things you don't like, and also recognize the lack in things you do.

All that said, I live with a former professional opera singer. There's nothing "effortless" about it, but being confident in your intonation leaves you more room for expression. But I get what you're saying about singers that try really hard and as a lousy singer myself, I appreciate your sentiment