Bon Jovi have never been number 1 in the uk charts. They got to number 2 with Always and number 5 with Everyday (they may have of had other top 5 singles but off the top of my head they are the two i can recall at the moment).
Now prayer is such a world wide known song that is played all the time at partys, wedding receptions etc that it is the sort of song that could be re worked and brought out to the public again that it would be a sucess and go to number 1 here in the u.k.
So yes if it were to be brought out IMO it would be HUGE