In his genre, he looked the best.
To me it doesn't matter his real life capabilities as a fighter. He had a magnificent physique, and performed his moves well for the camera, and most importantly made it look good.
I think that's the true strength of JCVD movies over his contemporaries. Seagal, while not as physically impressive, also made his skill look very good on film, but became less desirable to view with the weight gain.