I just think the stuff that makes Tekken good, could be accomplished in a much more intuitive fashion with better design. Certain things would really make Tekken more interesting, such as making throws start with the same animation so throw-breaking has to be a guess, and making movement cancels easier to bust. Intermediate-level Tekken to me is the most fun. I actually tried going to a few Tekken sessions of high-level folks back in the T6 days, but it was really frustrating due to all the movement cancels making the game look super-defensive to me.
It's also the fundamental difference between Tekken and VF- Tekken is more about spacing, VF is more about raw mixing up and conditioning (though conditioning does exist in Tekken) The threat of throwing is much stronger in VF which allows for more in-close mix-up, but at the cost of some of the positional game of Tekken. Oki is another difference- Oki is strong in Tekken, and more balanced in VF (though the 2d concept of meaty is very important in FS- especially for the character I use)
This is also why I think Tekken is much more popular, it's easier for 2d fighter folks to get Tekken's style of play, which is closer to traditional 2d fighters, than VF, which is much farther removed from the traditional model, and is more frustrating to learn/play.
Comparing the two is like comparing steak to cake. Both awesome, both very different.