Yes he was rivaling him. Yes he was instantly overpowering him in the duel. Gohan couldn't hold on, the moment it started, he was outright stated to be getting pushed back. Cell was laughing at him the whole time with a huge grin on his face and absolutely no strain on him.
Gohan meanwhile has veins popping all over him, sweat pouring down his face and is quite literally just a few pages away from getting blown away until Vegeta steps in. Gohan needs to use his full power to defeat Cell, Goku states that Gohan needs to release everything to win.
Prior to that, the poor kid was getting snot kicked out of him by attacks that weren't even meant for him in the first place. He completely underestimates Cell (and admits to it) and gets his ki, arm and willpower broken.
FP Cell could barely budge Gohan's head with his strongest punch. Zenkai Perfect Cell throws one blast and practically shatters Gohan. The same Gohan who thought he was going to rip Cell apart with his bare hands got his ass handed to him in a fight where Cell's entire focus was on Vegeta.
You were reading the same fight right? You do realize Cell wasn't rivaling 50% Gohan, he was about to annihilate him.
Chapter: 414 (DBZ 220), P14.2
Context: after getting hit by Cell’s attack while saving Vegeta
Gohan: “Cell’s power has gone up more than I thought…â€
Gohan outright admits he underestimated Cell, even Cell didn't try to act as arrogant upon his return. Now look what happened. Cell's threatening to blow up the solar system and Gohan's telling the guy to just kill him, having literally given up all hope.
Chapter: 415 (DBZ 221), P10.2
Context: after Gohan fires his Kamehameha
Piccolo: “It no use…! Gohan’s ki is weaker after all…â€
This is after his confidence has been built back up. Toriyama notes that ki is made up of different parts such as energy, courage and will power. Despite the fact that Gohan's courage and what not has been built right back up, he's still far weaker than Cell and can't do anything.
Goku: “Go strike with an all-out Kamehameha, like Cell! If you do that, you’ll definitely win! Absolutely!â€
Chapter: 416 (DBZ 222), P7.2, P8.1-2
Context: as Gohan and Cell’s Kamehamehas clash
Goku: “Hang on! Hang on, Gohan! You ain’t putting out all your power yet! Make your power explode!â€
Gohan: “I’m doing it at full force…! Any more than this is…â€
Goku: “Somewhere in your mind you’re thinking of the damage to the Earth! Don’t worry about it! We’ll undo the damage with the dragonballs!â€
Even on this part above, Gohan believes he's using his full power and its just that somewhere, almost on a subconscious level he's holding back. Yet Cell is still kicking his ass. It's made very clear that if Gohan wants to win, he literally needs to go all out and at least use his full natural power power to win if not outright dig into his deep bag of potential and rage and bring out even more power.
You think Cell doesn't rival SSj2 Kid Gohan? Because all the evidence points otherwise.
And you think Dabura who is barely shown to be above a far weaker SSJ Gohan (Yes, Super Saiyan considering he shows no signs of any SSJ2 characteristics) rivals that same Cell.