While a Lion is indeed a powerful and dangerous predator, a gorilla is as equally powerful and more capable opponent. While gorillas spend much of their life foraging, they are more than capable of using their natural abilities to defend themselves effectively against the limited arsenal of the lion. The gorilla's thick hide will protect him against the teeth and claws of the lion while his powerful arms could easily cripple a lion in one shot.
I believe that a gorilla would win a fight because it seems in this wourld of ours that monkeys or types of monkeys (Gorillas) are more intelligent than lions, have more strength, they might not be as fast but it seems that it doesn't really matter about fastness. So over all i believe a gorilla would win a fight over a lion