1. Bill Gates
2. Larry Ellison
3. Jeff Bezos
4. Sergey Brin
5. Larry Page
6. Steve Ballmer
7. Paul Allen
8. Michael Dell
9. Laurenne Powell Jobs (widow of Steve Jobs)
10. Mark Zuckerberg
If the definition of old is "younger than 20 years", this represents 3 startups (Amazon, Google, Facebook). If the definition is "younger than Skype", then only Facebook is left.
I was more interested if younger successful founders in the US faster take-over older founders. And they don't. A large part of the wealth of the older founders has been acquired past-IPO.
The conclusion (for me) is that to make it into the top 10 (whether US or Europe) and stay there, you gotta grow a company successfully for many years, like Microsoft, Oracle or Apple did in the US and SAP did in Europe.
Discounting the Samwers for obvious reasons.
We suck compared to the US regardless of how you slice billionaires lists.