Has all the martial talent in the world, doesn't train.
Yeah yamcha is lame, but he realizes he can't compete and bowed out from the game after things got serious around the android/cell saga. I can't hate on him for that. Gohan on the other hand...can compete if he truly wanted to, he could very well be the strongest, he has the talent to make it so far, but he just don't want it. Gohan is an infinitely better family man than goku, but as a warrior and z-fighter he's so disappointing.
How you get one shotted by base frieza? You didn't want to train at all young simba?
How you have all the talent in the world but none of the drive to put it to use? If he wanted to, he could be on par with Goku and Vegeta. Doesn't he know cats like Tien and PIccolo would kill to have his genetic potential? Gohan, you ain't a fighter. You just a dude who fights. Gohan is that dude when he needs to be, but he just ain't a real saiyan. He's just a powerful human.