Reddit, I'm 28, have a comfortable life but I'm starting to feel like I'm missing something. What do you suggest?

So... I have a decent career, an average-to-nice income, a nice apartment, a nice girlfriend (we live together), two nice dogs... but recently - for the last few years - I've started to feel like there's more to life, like I'm missing out on cool stuff in the world.
I'm not an outgoing person, so I spend most of my free time playing videogames, watching movies, reading books, the usual nerdy stuff. The girlfriend is a lot like me so we usually do these things together.
I'd like to travel more, but I don't like the usual 'touristy' stuff so maybe ideas in that area would be nice. Keep in mind that I don't live in the US, though. I'm in South America.

What other things would you do? I'd just like to feel like I'm enjoying life, like I'm seizing more of what the world has to offer.

tl;dr: life is good but boring, suggestions would be nice.

excuse my bad English.