If a pessimist was usually right, wouldn't that make him a realist?

A pessimist is an informed optimist.

A pessimist is that who before crossing a one-way street looks in both directions of it.

I'd say this was strictly true only for those pessimists who feel a need for validation.
Could one not equally say 

An optimist is someone who is pleased with good experiences because they show he was right.

In either case, it seems to me to be more focused on the pleasure derived from being correct, which is neither a defining trait of a pessimist nor an optimist, so no, I don't agree, as the labels of pessimist/optimist only deal with the expectation. The reaction to an event turning out negatively will, I'm sure, be varied.

Perhaps a good question would be 

If a pessimist is pleased by that bad experience, is it still in fact, a bad experience?

Some correction guys!  Igor, you should say "A pessimist is a man who looks both ways before crossing a one-way street." Mi Sha, you should say, "A pessimist is a well-informed optimist." By the way, does this quote belong to Mark Twain?