Such interesting postings re this subject. I venture that it all depends on who the singer is and why they sing as they do. I was just trying to imagine 'Wigan Pier' being sung by Jessie Matthews in her 'own voice' as she eventually produced it.    Somehow for me that does not work. I need the accent, or the song doesn't work.
I also can't imagine a trained tenor singing 'Wur can that blackbird be, wur can that blackbird be??' etc etc etc.

At present I almost exclusively listen to Asian singers and music and watch Asian film etc. Must say I am not sure where the Peking opera would fit in this discussion. It all depends what sounds you like to hear.   Same with Korean Pansoori singing.

And then there is always a good Welsh Male voice Choir.