Base used to be relevant but that was back in the old days. In modern MMA, you have to be well rounded to succeed.
good example of that is Palhares. He could be top 5 if he developed some decent striking.
Fedor, Mir, Lytle, Serra, Hendo, Chuck, Minowaman, Maynard, Forrest, Hunt
Pickett, Cerrone, Matt Brown, Bisping, Weidman, Barnett, Lawler