I should have clarified: the revolutionary part is that through the possession of data (private keys), users are able to lay claim to their units of cryptocurrency.

Monopoly money is issued by Hasbro (private institution), can be fairly easily counterfeited, has little to no acceptance outside the context of a board game, and there’s no upper limit to how much can be printed. On top of all that: there’s no cryptographic way to prove the validity of Monopoly money and it can’t be transferred across the planet as easily as sending an email.