Tekken 3, for me, was truly the creative peak of the series.
Incredible music, Law's fucking BAD-ASS yellow jumpsuit.
I loved the way they ditched many of the clone characters and brought them back as more developed characters with cool styles (Baek=Hwaorang,Bruce=Bryan,etc.)
Xiaoyu and the shitload of Lei stances were just icing on the cake.
Ogre and True Ogre were the best bosses of the series too.
T-Tag was a misstep for me, I didn't like the tag gameplay, and I hated the way all those clones came right back. Tekken 4 isn't even worth talking about.
Despite all this, I still overall love the series and have massive nostalgia, especially for T3 (when it was big in the arcades in 1997 when I was also with my first serious GF.)
Hopefully Tekken 5 will resurrect the series. Namco needs a comeback.