Do you think the sex alone makes it all worth the time and emotional investment?

Yes, I do. In my opinion, people in general underestimate the sense of emotional fulfilling that good, regular sex has on the male brain (I'm assuming you're male).

Separately (and now we're getting completely hypothetical), what if sex was unavailable or impossible, would it still be worth it to you?

That would depend more on how challenged you are to find a suitable partner, I would still say yes, but in a narrower range of investment.