From Sunlight Yellow:
The 5th “King of the Iron Fist Tournament” has ended with Heihachi Mishima missing and the eventual winner being Jin Kazama.
Jin Kazama then assumes the role as head of the Mishima Zaibatsu and beings using the special Tekken force units for propaganda and manipulative acts all over the world. Eventually many people become upset by this and it starts riots and eventually war amongst nations.
With the world now at war, many nations lose their power and the Mishima Zaibatsu declares itself as an independent nation.
The Mishima Zaibatsu is intent on conquering the world with only G Corporation to stand in its way. People around the world see G Corporation as a savior and G Corporation offers a price on Jin Kazama to anyone that can bring him in alive.
Just as anyone could have expected, the announced for the 6th “King of Iron Fist Tournament” was under way.
Those that want to make a name for themselves, those that seek money, and those that want revenge. Many different ideals and goals gather while the Tekken 6 tournament is unveiled.
Well, this completely changes up the storyline. Jin is far from good now, borderline Black Adam level. Heihachi missed the entire tournament because of the Jack attack (HA HA), so he's stuck in Tekken 2 mode, Kazuya is still a bad guy, but is working with people who are considered good, and the rest of the cast (san a few like Yoshi) have had their lives radically altered.
I guess the only ending that mattered was Jin's in Tekken 5.
That said, I like the change. It makes the storyline a bit more complex than per se a few Tekken cast members (Jin) vs some evil person. That, and at least it has a somewhat good storyline, something every fighting game except a few like the stillborn franchise Guilty Gear seems to have a problem with (Virtua Fighter being the biggest offender).