If you like 4x games, I would suggest X3:Terran Conflict/Albion Prelude from Egosoft. Its older, so wont be a burden,(CONTROVERSIAL OPINION ALERT) and probably the last good game from egosoft (/CONTROVERSIAL OPINION ALERT)

Space game set in a huge world with multiple factions and in a breathing world that can and does change with time with or without your actions.. hundreds of hours of gameplay, with options for building your own empire.. and its got a huge modding scene that can make it even more alive.

Once you start getting your personal economy going, you can take a more macro chill approach to the game, you can sit in a mothership issuing fleet commands and letting the AI handle everything, or you can get right into the cockpit of a corvette/fighter and dogfight yourself. While building massive station complexes to produce goods to sell and generate funds with.. or to build your own ships and fleets with.