If it's based on stats to the nearest rival Don Bradman is the greatest.
Bradman is no doubt the best batsman and cricketer of all time, but to regard him as twice as good as anyone else is slightly misleading.Anyone who understands basic statistics and understands most sports would never disagree with this statement. Since we're on a tennis forum, I'll give the following comparison - for Federer or Nadal or Djokovic to be even considered equal to Don Bradman, they'd need to win something like 24-30 Grand Slams. Just shows how amazing Don Bradman was.
One must look at the quality of opposition, and the portability of his records - Bradman only ever played in Australia and England. Never the subcontinent on their home spin friendly dry flat turfs, the West Indies against fierce 4 pronged pace like in the 80s, South Africa etc - ie places where you may get more outs and lower scores, that may actually bring your average down.
Shane Warne would be his equivalent as a bowler.
Of course the Don did not bowl, or rarely bowled, so the durability of being an All Rounder is not there either.