Since it's extremely difficult to be -the- best in the world at anything, I've found it fun to look at a particular combinations of skills that you're likely the best at.
For example:
1) Soccer. Played competitive soccer all my life, including in college. While there are tons of people better than me in the world, I'm still better than more than like 99.9% of the world (this includes men who play soccer, men who don't play soccer, women, and children, so that figure really isn't all that unreasonable)
2) Gen 1 OU Pokemon. Played since 2003, know all the ins and outs, and probably in the top 10 battlers left still on the site. I was far and away the best on the ladder last time I played, about a year ago, staying at #1 for a few months. Though I'm sure many of the older battlers at least tie me on skill level. I beat the site owner (and good friend) chaos on a regular basis. He sucks.
3. Being white. Only because husk or reyscarface could possibly pose a challenge to me on the first two. But I knock them out with this one. As well as any good Japanese soccer players who are closet online pokemon players.