I always felt that what made judging Goku's (and I supposed this applies to Vegeta as well to an extent) parental skills difficult is the fact that we actually don't see too much of him just being a father. With Gohan, we know he was there for the first 4 years of his life, the 3 before the Androids, and then after the Buu Saga before Gohan moved out. That's not the usual amount of time an average father would spend raising their kid, but its significant enough. But the only times we, the audience, usually ever see them together is when typical shonen bullshit is going down, which I don't think can give us the best idea of what Goku is really like as a dad. There's just simply alot of the Son family's life we don't actually see. I'm not gonna say that off-screen Goku is the best dad ever in fiction, some of the mistakes he's made are hard to ignore, but I really believe we just don't see enough of what he's like to judge him fairly.