X3 Reunion was the game that pulled me in to the series. Had a pretty big "transport company" going.
Some spaceweed station... Hey, easy money.
Made quite a lot of money with universal traders and some stations.
A couple of years before that, I tried X2 The Threat which I got with a graphics card. But it felt too complicated at the time.
Bought Albion Prelude after reading the first impressions of Rebirth.