The standard response to that is "the market can stay irrational for longer than you can stay solvent."

It's a nice line but I think if being more 'rational' than the market causes you to lose all your money then you're doing 'rational' wrong. Rationality is supposed to be about winning, not about being 'right' but broke.

What historical rate of return on investment = rich?

Consistently displaying positive alpha over 5+ years would be indicative of some genuine investment skill. Some top hedge fund managers seem to be able to do this but it is a pretty rare level of talent.