I need to provide a formal paper on why Gon is boring? Are you fucking real?
Ok, fine. For a character solely motivated by revenge, he's taking his sweet time trying to get to it. There's no drive in his actions or the plot. That's what I mean by glacial pacing.
And besides, Kirito is less a fleshed out character so much as he is an audience surrogate. A guy who plays vidya games to save the day and have women fawning after him. He's less a character and more a power fantasy which is why he tends to be popular with teens. His Sue-ish tendencies aren't a bug, they're a feature.