Goku knows Gohan isn't a fighter like he is and isn't with his heart there. In peaceful times, Gohan prioritises studying... That's what he likes to do. He's only on battle mode when there's danger looming in. Gohan seemed very dedicated based on the library there was on his house... Goku wants someone who wants to get stronger and knows will be full time commited to the training. He wants to battle with someone who's with their heart on fighting. Having a full on battle vs developed Oob can please Goku whether he's above or below Gohan. He just knows what his son is passionate about, he won't force him to be a training partner for a training and battle maniac like him which does it except when eating and sleeping. He also had a close call vs Kid Boo... He wishes he can battle that kind of being, although gentle, as a way to measure himself in light of his improvements giving that person the condition to compete when getting stronger. He knew Gohan was way above himself there, when Kid Boo was about to be killed, yet he wanted to "settle" things nicely vs him when he'll been training hard for it... That happens despite the fact Gohan was above Kid Boo. Kid Boo picked Goku's interest just the same.
It's like Goku being all pumped up to fight Oob in the Tenkaichi when he expected to fight him in base... Gohan would obviously be way beyond base Goku there but he didn't even participate in the Tournament. He wished to fight Oob there knowing of Gohan's power and knowing OOB would be ~ his base there, knowing Gohan's unwillingness to compete because it isn't in Gohan to be fighting... His interest can be sparked regardless of how they measure to Gohan. Goten was kinda forced to enter the Tournament but maybe Goku sees him wanting to date as lamer than Gohan's more justifiable academical life, plus he's still below 18 years so Goku can be more incisive lulz.
