Yeah, all they need is to make the ESRB universal. It does the job fine.
The only problem with that is countries like Australia and whatnot ban the sales of games with certain ratings. As we all know, censorship is the opposite of freedom; it is slavery. Hopefully having such a rating system internationally would allow video games of all ratings to be sold without worry for censorship, and this would also lower the cost of localizing games, which could potentially mean we'd have one less huge reason not to release a game internationally!