First, Google. Then, if one side is unhappy, a judge. Example: this article.

What exactly is wrong with judges making decisions? Seems to kinda be their job.

This means that any time someone is unhappy with the decision, Google (or an other company) has to shell out tens of thousands of dollars in legal fees. Maybe Google can keep doing that for a few months but a normal startup would just grant every single request rather than having to fight it in European courts.

The decision should be made by some independent privacy committee which reviews all the facts, and right to be forgotten requests should go through that committee rather than directly to Google