I rhink the strongest is akainu, magma would always beat ice, he survived the fight with whitebeard, then with croc, then with marco and the admirals. Also, i repsect his will to continue to fight, and his crazy absolute justice.
There is also his succesful plan that turned squardo agaisnt whitebeard, he is a military genius, where aokiji is lazy, and kizaru is laid back.
Its also possible that the three admirals would be completely equal in strenght, just like rock paper scissors. Lava beats ice, ice reflects light, light destroys lava. If so, their strenght is reflected on who they fight?