Going in circles here!
Their decision to sing in a phoney, pseudo-American accent disqualifies them for being considered great in any way.
Let's try something else.
Imagine there was a painter who had a very good technique, and he created a piece of art in the style of, let's say, Van Gogh.
Now, this painting could be so well executed that, unless you were an art expert, you would be fooled into believing that it was a genuine painting by Van Gogh.
Would that mean that the artist, who painted the "fake" Van Gogh, should, in anyway, be considered the equal to, or indeed greater than, Vincent?