I know nothing whatsoever about opera, but I do remember reading that in terms of being a good opera singer, Paul Potts is actually average, but of course, the majority of voters know nothing about it, the same as I don't.
I have been aware for years however, that the power of the song can give a false impression of how good the performer actually is - people get carried away by the emotion of what they are hearing, which more than covers up any lacking aspects of the performer delivering it.
Two fine examples of that point are Paul Potts singing Nessun Dorma, and Alexandra Burke singing Hallelujah.
The simple fact is, I could get on stage and sing either of those, and get tears from audience members, but that would be entirely to do with the majesty of the songs, and nothing at all to do with my seriously lacking vocal talents.