weii,to tell you the truth Gohan is not a great fighter after all,well he relys only on his rage power,or else he is weak.Gohan might have defeated Vegeta,Frieza(3rd form),Cell(3rd and 4th form),Super Buu(2nd form) only because he is angry thus giving him the rage power.fyi,it was not Gohan who defeated Cell's final
form it was Vegeta.because Vegeta was the one who found Cell's weakness.(in his head).thus blasting it and Cell was killed.