Life is full of surprises.
I thought I knew exactly what 'nymphomaniac' meant in etymological terms, but just found this in Merriam-Webster:

Etymology: New Latin, from nymphae inner lips of the vulva

Conclusions:
the overall male equivalent for a 'nymphomaniac' would be a glandimaniac (sp?)

However, if we limit the field to heterosexual males, the equivalent to 'nymphomaniac' would probably be 'nymphomaniac'!