I liked Starpoint Gemini but don't care for #2. It is nothing like Freelancer.
Origins is Starpoint Gemini's campaign superimposed on Starpoint Gemini 2. Secrets of Antherea, the only bell that is ringing is that it seemd short. The SG2 campaign also felt short and like it was cut off mid-sentence. I haven't played Titans...bought it a while back though. I know that it is end-game content and you get one of three ships by completing quests for their respective faction.
Origins I thought was better than the SG2, and because it is eaiser to level up, Origins is better than SG1 campaign (between every story mission, you'd spend forever either leveling up or moving between sectors to get to where you need to be). Beware of bugs in Origins though. For example, reaching a waypoint before you're supposed to could break the campaign. You'd have to reload a save and take it slow.
Frankly, the only thing I'd say is worth playing is Origins in SG2. The rest of SG2 isn't really worth it.
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