@indeedcodybrown: I think your right about Dan watching Cowboy Bebop. It's completely built around Western culture and Western cinema.
Dragon Ball Z is too slow for him. Just like he says with his dad and friends, if he want's to show something to someone he makes it easy for them to get into it. Dragon Ball is difficult to get into when someone already doesn't like animation, then layer anime, the stigma of anime, and then layer on like 6 full episodes of nothing but charging an attack?? The barrier to entry is way too high. I think it's the same for all shounen anime too. They all suffer from massive filler and ANY filler would be a much more significant blow to Dan's already shaky motivation.
Cowboy Bebop is a short length, concise, has action through out and it's based on Western actors and movies. For him specifically that is a MUCH lower barrier of entry.