You don't need to play them all at once, haha. You can start off with one of them 6 months to a year later, that's how I did back in Tekken 6. After playing Tekken 6 for 10 months, I started playing Soul Calibur IV, but I lasted with it in just 3-4 months before I came back to Tekken because Soul Calibur is an easier game to learn than Tekken because of its more straightforward game play.