xavier is one of the 7 smartest humans on earth.
i think this is the list:
-reed richards
-henry pym
-david bruce banner
-charles francis xavier
-anthony stark
-jose santini aka the mad thinker
-amadeus cho
--------------------------honorable mentions--------------------------
-victor von doom (most likely was left out due to his at the time criminal status)
-nathanial essex - believed dead for many years. general humanity are oblivious that he is mr. sinister
-herbert wyndham aka high evolutionary. like essex he is believed dead for at least a century and the general public is oblivious to his existence.