As others have alluded to, I tend to respect the ones that have kept their girlfriends/wives before billionaire status more than playboys after (but this may be a societal thing that has been ingrained into me).
3 big things here:
1.) When you go through a powerful experience with someone, you form a greater a connection. Imagine having a girlfriend for a year. She makes you feel warm and motivated, and you push through working hard on projects, and she supports you and motivates you. Even if she is in the shadows, it feels like a "team" and like you experienced "greatness" together (isn't that why women prefer high status men?). This can form a very strong connection, just like if you and a lover survived a plane crash together on a remote island or something.
2.) It's difficult to trust women (and men) after becoming a billionaire. Who is using me? Who really likes me? Is she going to keep asking me to buy stuff? Does she expect a diamond ring every birthday? Crap like that.
3.) When you're in the spotlight, all of that fame/attention can be tough on your dating life. If you're a "secret" billionaire (i.e., not that well known), then it's probably amazing. But, if you go and ask out a bunch of women or try to have sex with a bunch of women and then they tell reporters, this is going to hurt your reputation. You have to evaluate risk-of-reputation vs. sex-drive. Will people still want to do business with you? Will girlfriend-material-type girls want to even agree to dates?
But, I do think those women are fairly unattractive (Jeff's, Mark's) or just plain/average (Sergey's, Bill's). Zuckerberg's probably makes the least amount of sense because I don't think he was dating her before the billions, but I may be wrong here?
Lastly, check this site out:
http://www.therichest.com/rich-list/world/the-hottest-wives-and-girlfriends-of-billionaires/
Ideally, you'd want to be a secret/lesser-known billionaire or live in a country where you're not as well-known and still able to flaunt your money around (but not overboard to reveal identity).