Alot of the posts on this thread are amusing due to sheer ignorance of the meaning of the terms being used. Specifically the word "Kung Fu".
I don't think alot of you realize what "Kung Fu" is. "Kung Fu" or "Gung/Gong Fu" directly translated into English would roughly mean "Hard Work" or "Work Hard" (and other variants) depending on the context and use.
When the term "Kung Fu" is used within China it's reference could be vast and doesn't even have to apply to any martial arts what-so-ever. As an example: I had a friend that was in China recently tell me that he saw signs posted for some hiking trails in the woods one day. The degree of difficulty between the paths were differentiated using the phrase "Kung Fu" in their descriptions (As in: "...This trail will require more "Kung Fu" than the other...").
So to say that MT, or BJJ, or Judo, or Karate or "MMA" is any better or worse than "Kung Fu", what you really are referring to, after a fact, is the degree of "Hard Work" that particular practitioner puts into their training!
Put another way: IT TRULY COMES DOWN TO THE INDIVIDUAL, THE EFFECTIVENESS OF THEIR INSTRUCTOR(S), AND THE DEGREE OF "HARD WORK" THEY PUT INTO THEIR TRAINING.
As long as the curriculum any given student is following is practical and rigorous enough, and as long as the student themselves train HARD, and their teacher or school continually pushes them to the next level to be able to effectively execute their movements in real-world combat situations, you are going to get a superb fighter no matter WHAT the lineage or "style".
With that being said, you could consider, after a fact, THAT ALL MARTIAL ARTS ARE "KUNG FU":
They all take a tremendous amount of HARD WORK to make effective for any given individual; no matter what the style.