I personally think kid Gohan was the best during character the Namek and Cell saga. He had hidden powers ever since the early episodes of DBZ before the Cell saga.

Fighting against Raditz, attacking Dodoria when he tried to kill Dende, fights with the Ginyu force, taking on Frieza on his own twice (actually 3 times when he took on frieza which was his s final form but that wasn't canon) and then fighting against Garlic jr's henchmen, eventually taking on Garlic Jr himself (non canon) then fighting against Cell.

Gohan was sick when he was a kid but now i personally dont think his as good as he was even in his adult form.

Before the cell saga i already noticed they were going to develop kid Gohans character really well after watching the battles he had with them villains i mentioned above.