First, so I can show up in the 3rd or 4th installment of a future civilization's video game franchise as an "Ancient One" and speak in hexameter.

The middle one. So that we have plenty of younger civilizations to teach and kick around the block if they misbehave. But also so that we have some Ancient Ruins to discover and learn about Meaning of Life from, triggering all the good feels I usually get at this point when watching sci-fi shows.

I believe aliens have no reason to not genocide us immediately upon discovering us, so I'd rather be the only civilization.

But to answer your question, absolutely the first. That way, if we are more benevolent than the Machiavellian necessity, we will either pioneer an improbable United Federation of Planets or be eradicated due to our idealism and naivete.