Hmm.. I've played most fighting games and what I can say is that I like Soul Calibur the most, then comes King of Fighters, and then.. well... then all the rest.
I like Soul calibur because of the art style and.. well.. the weapons, levels, characters and the possibility to design some yourself. Seems to be just my taste. And that it not has what I dislike about Street Fighter:
I disliked about the "recent" Street Fighter games is that there were those completely silly combos, that just killed you, once started. People who were able to do those were impossible to beat for those who weren't, even if they had equal or better reactions, etc. Just because they were not able to produce an flawless stream of button-combos. Sure, that is always a part of beat 'em ups, but it shouldn't be everything that counts. At least that was the case with some Street Fighter Alpha I played.
What I dislike about Tekken is that it just is so painfully slow. Seriously, play a round of KoF or Street Fighter, followed by a round of Tekken. Feels like slow motion.
On the other hand, if you have a girlfriend, this might be the right beat em up game to play together. And I mean this in a positive way, as you can still have fun with Tekken, of course