If you want to compare, you should make the cutoff be based on net worth, not simply take the top 10. Then you also get eBay, Tesla/SpaceX, Salesforce, LinkedIn, Yahoo, and Square/Twitter among others.
Sorry, re-reading my post it was misleading because I didn't post my intention: I did not want to show that Europe is coming up with successful start-ups at any rate comparable to the US, SV obviously wins by a huge margin.
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.
Yes, the thing that always strikes me about the Forbes 400 is how old so many of the people are. Clearly the normal way to end up super rich is to have something that grows fairly rapidly, and then give it a long time to grow.