You are going away, to some place isolated… in space, of course. You will only be around one other person. You can take an allotment if 1GB of personal media with you (text, video, music, games, pics, etc.) that you will be able to access in your free time indefinitely at will.
The other person will also take 1GB with them, but you won’t be able to talk to them until you’re on the journey.
You will have access to any knowledge resources to perform your function and keep you alive. You will never return to a point where you can get new external media. Any additional media you ever access would have to be created by you and or your travel partner with what you have access to.
You will also not know the sex of your partner, but they have willingly taken the same risks to embark on the journey as yourself, and will have a similar mission.
When you take file sizes into account, EBooks are the most high-density entertainment you can bring. Followed by old-school games, then music, then video.
I would probably choose my favourite movie in SD, a few dozen of my favourite songs, a few dozen old school games, and then fill out the rest with a few hundred ebooks.
Variety can be way more valuable than pure quantity.