I just found this old post by Norm about a pretty cool idea:
"Some of my friends engage in a friendly contest: they compete to see who can visit the most countries. It’s a life-long game. One of the sub-goals is to always have visited more countries than you are years old."
If I am not missing any (not quite in exactly the right order, I fear):
  1. Switzerland
  2. France
  3. Italy and Vatican
  4. Germany
  5. Spain
  6. Belgium
  7. Poland
  8. Austria
  9. Czech Republic / ex-Czechoslovakia
  10. Hungary
  11. Turkey
  12. Egypt
  13. Cyprus
  14. USA
  15. Canada
  16. Kenya
  17. Tanzania
  18. Peru
  19. Morocco
  20. UK (England and Scotland)
  21. The Netherlands
  22. China and Tibet
  23. Taiwan
Here are a few candidates for the next ones:
  • Mexico
  • Japan
  • Greece
  • India
  • Nepal
  • South Africa
  • Congo
  • Brazil
There are currently 193 countries (well, "states"), 194 if you count Taiwan (and really it should be counted). This means I have 171 countries to go to be done (countries popping up or disappearing notwistanding), and starting exactly today, I have 12 to go to catch up ;-)