Well if we're strictly talking about self made income then Gates and the other top forbes list will be in it. But if we're talking about juat plain old cold cash and asset then i would guess the saudi princes and sultans with oil fields to their names. Rothschild and other conspiracy theory families and corrupt officials.
Gates may not be comparable to Arab princes or sultans with all their assets, imagine many countries such as America and Russia are fighting over Arab territories because they are rich in oil, how rich Arab princes have that assets, even if you look at their lifestyle, it's very glamorous with thousands their luxury cars are carved
I don't think they were much rich when compared to other person as individuals because they are governments and it is not the money earned by them so I don't thinkk they will be the richest individual person and even most of the politicians from the third world countries living the same life as the arab pricess do because they have corrupted money but they can't be reported as most rich because they will be in jail if they get caught.