Hmm, best informed investment? I think in this case there is a little more in play than just extreme luck.

What happened to the guys who bought Manhattan for beads way back? Did they make it ok?

We can be sure, mathematically, that a lottery ticket is a bad investment overall even if it pays off. For example, repeating it 100,000,000 times is nearly certain to leave you with less than you started.

Plausibly, the decision to invest in Facebook (and similar opportunities when they present themselves) had a positive expected return at the time. Even knowing Facebook is an outlier result -- like a winning lottery ticket -- its payoff actually gives us a hint that the original decision was positive-expectation, and its magnitude. (The fact that a lottery ticket happens to win changes our idea of the original expectation not at all.)

Also of note: Thiel didn't just invest money, he invested his expertise and network. That, which almost certainly helped Zuckerberg aim higher and avoid pitfalls/compromises that took down other companies, was one of the best non-monetary investments ever.