Rude, Johnny, Barret, and while we're at it, hey why not Sephiroth?
Because none of Rude, Johnny, Barret, or Sephiroth has ever been implied to share mutual feelings with Tifa.
She has never been called an important woman to Rude, Johnny, Barret, or Sephiroth, nor has she been called the mother of the family unit with Rude, Johnny, Barret, or Sephiroth, or said to be part of a family unit with any of them at all.
Furthermore, two of them have never even had the remotest hint of feelings towards Tifa, and of the two who it has been said their feelings are futile, making the statement that Tifa is someone's beloved utterly meaningless information in an otherwise information laden tome.
To sum up, It is parsimonious that the person for whom she fulfills the role of beloved is Cloud. It is not parsimonious for it to be anyone else.