Tsk Tsk Tsk. Sorry, but I think you forgot very important details in regards to Initial Goku's power.
Chapter: 391 (DBZ 197), P1.3-4, P2.1-4
Context: talking about the Room of Spirit and Time
Vegeta: “Well, well…So even the great Kakarot admits defeat against the rigors of that room…”
Goku: “Maybe…But pointlessly toughening up my body more than this is just torture, not training. But I won’t object if you guys enter that room again. It looks like you still have room left to toughen up more.”
Vegeta: “What was that…? I don’t like that…The way you said that made it sound like you’re saying that your true ability is greater than mine…”
Goku: “Yeah, a whole lot greater, I think.”
If Goku at 25% of his power rivals Initial P.Cell, someone who easily tanked his kick, how in the world would Vegeta be doubting Goku's abilities to defeat him? Note that Vegeta's states true ability, implying the Goku that he is talking to right now is inferior to him. Even the Z-Fighters were surprised when Goku said that he was much stronger than Vegeta was. That True ability that was mentioned was probably 50% Goku which was the whole notion of why everyone shat their pants.
Vegeta (to self): “Damn you, Kakarot… It’s always like this… He’s always a step ahead of me…! It drives me crazy…Just when I think I’ve caught up, he widens the lead again…”
Dont you think he would have said this if Initial MSSJ Goku was stronger than him? Instead, he said this AFTER Goku powered up.
Based on statements
SSJG3 Trunks (In my opinion) >> Initial Perfect Cell ~ MSSJ Goku (50%) >>> SSJG2 Vegeta > Initial MSSJ Goku