Goku. He's the shows protagonist and the one who everyone always relies on. He's the hero of the story, the most selfless and Cell aside the one who always ends up saving the day. Speaking as someone who normally doesn't like the main character he has a lot of qualities like his selflessness, humility and at times stupidity which make it difficult not to root for him. He is in my view the most universally likeable main character in any series I've seen and my favourite by far in DBZ.
Gohan by contrast is not one of my favourites. He comes across as a bit of a wimp with no real battle sense, the random gargling noises kid Gohan tends to hit out with every 10 seconds were a particularly annoying reminder of this. He is lazy, doesn't train and gets most of his significant power increases handed to him on a plate. In spite of this he still has a tendency to become arrogant when he has th upper hand in battle and this pretty much always costs him. That kind of things fine if alongside it the character has an edge like Vegeta but Gohan's arrogance alongside his goofy attitude is a strange fit and a major reason why i'm not a big fan.