Chapter: 437 (DBZ 243), P11.2-3
Context: talking to Goku
Kaioshin: “I’ve managed to pass the preliminaries too. It’d be nice if the match-ups allow me to have a match against you. Of course, I don’t have confidence that I could win, but I want to know just how strong you are.”
As the highlighted part proves, Kaioshin doesn't have any idea how powerful Goku is at the moment. In order to find that out, he has to fight him. But based upon what he's seeing, he doesn't think he can win. The following three statements help to surmise this as an absolute fact:
Chapter: 438 (DBZ 244), P5.5
Context: after Gohan gets matched with Kibito in round 1
Goku: “You’d better not let your guard down. I don’t think he’s just some regular joe.”
Gohan: “Y-yeah…I get that feeling too.”
Chapter: 443 (DBZ 249), P9.1-3
Context: as Gohan prepares to fight Kibito
Gohan: “Man, this is a predicament. Bulma told me that if people found out my true power, there'd be a big commotion and it'd become hard for me to go to school anywhere. That's why I disguised myself, but...He doesn’t seem like an opponent that I can beat while suitably covering up [my true power].”
Note: That last sentence is one of those that’s kinda hard to translate literally. “Covering up” (gomakasu) is in the sense of faking it or deceiving someone, not simply in the sense of wearing a disguise, and in context he's almost certainly talking about covering up his true power (since that's what he mentions disguising himself in order to prevent people from finding out about). So essentially, Gohan doesn’t think he can win while still covering up his actual power. Hence Viz’s ‘by accident’ being in quotation marks: they mean the sort of thing Shen did, hiding his power by making it look like he won by pure accident. So I can see what Viz was going for with their translation, but I think it is kinda confusing.
In the first statement, Goku is basing his estimates about Kibito's capabilities sheerly on his appearance alone. In the second statement, Gohan is doing the same thing towards Kibito and ascertains that he is unable to win. So it's factual that Kaioshin is doing the same thing to Goku because he states that he can't win and follows up with '
but I want to fight you to see how strong you are'.
Additionally:
Chapter: 334 (DBZ 140), P7.3
Context: seeing Super Saiyan Goku
Yamcha: “Wh…what ki…and he’s not even fighting…”
This evidence should solidify the fact that Kaioshins remark wasn't entirely based on Goku's Ki reading as opposed to his appearance.
Even if this isn't enough for you, let's move on and throw more evidence on the table shall we?
Chapter: 443 (DBZ 249), P9.4
Kibito: “Become that ‘Super Saiyan’ thing! I want to test you to see if you really will be able to help us.”
The Kaioshins are already aware of Super Saiyan and Kaioshin himself is expecting this. So even if he doubted his own capabilities against Goku, he would still have 'expected' Super Saiyan and it would logically expect it to result in an increase of battle power, probably surpassing his own.
Even so:
Kaioshin: “…No, even so this is magnificent energy, more so than I imagined…I wonder if I’ll be able to stop this power…”
Kaioshin '
imagined' this (
Super Saiyan) level of energy. But he doesn't fully comprehend how powerful it is until he actually sees it. So even if you with to ignore my original contention, I can counter you with the fact that he was also factoring in Super Saiyan when he regarded himself as inferior to Goku.
P.S.
I'm making all these threads to use as counters to people who disagree with the 'Freeza > Base Goku' statement.
