Defending Their Kid:
Goku: Sacrifices his own life (multiple times, mind) to save not only the world but, more importantly in his mind, his son.
Ozai: Would sacrifice his son for more power.
Point: Goku
Teaching Their Kid:
Goku: Teaches son how to train, fight, and generally maintain exceptionally good physical health in between studies (note that Gohan turns out to be a scholar, not a fighter). He also clearly knows his sons abilities and limits, and uses that knowledge to bring out the best in his son. Throwing Gohan against Cell, Goku knew for sure that Gohan was going to win. Keep in mind that Goku's entire starting fight was to make sure Cell's power was where he thought it was, and that Gohan could actually beat him.
Ozai: Burns his own kid's face, doesn't teach him much of anything once he realized Azula is the more powerful, generally ignores Zuko. Not only that, but he taught Azula to be batshit crazy.
Point: Goku
Abandoning Their Kid:
Goku: In the process of sacrificing himself to protect his son, he leaves his family behind. He also ensures Gohan has a father-figure in Piccolo, and Chi Chi is more than capable of taking care of a house by herself.
Ozai: Kicks his kid out after disfiguring him, then banishes him from all of his friends and family. Iroh accompanies Zuko because he doesn't want to abandon his nephew, not because Ozai does anything to help his son. In fact, the only reason Zuko was able to get anything done at all was because his uncle still had influence in the Fire Nation. After years of being gone, Zuko is only accepted back because Ozai believed he killed the Avatar (keep in mind, Goku strongly encouraged Gohan's passivism). Not only that, but Ozai wasn't there for Zuko during his childhood in the first place, despite not being dead like Goku was.
Point: Goku
End result is Goku is a better dad, hands down.