Good comment. I would add that our Sun is alone, while up to 85% of solar systems are at least binary. It's possible multi-star systems make life more difficult. Similarly, Earth's magnetosphere may be uncommon, since we don't see a similar one on Mars or Venus. And maybe Earth's rotation is uncommon and many planets are tidally locked.

I wonder, though, how this stacks against the sheer size of our galaxy. There are 100 - 400 billion stars in the Milky Way, including about 4 billion Sun-like stars. Plus we keep revising estimates upward when it comes to exoplanets. Recent observations seem to indicate that 33% - 90% of Sun-like stars have rocky planets at a distance where liquid water is possible.

Are features like an unusually large Moon or a protective gas giant so rare that our planet and solar system are truly unique?