Wow, Dragon Ball, I totally forgot about that, it hasn't been shown in years here. On German TV they show Pokémon three times a day, episodes from different seasons. Honestly I'd be happy if they would start showing them from the beginning again for a change, I haven't seen the Kanto ones in forever.
As for the popularity, if you're not into the games in particular I don't see any reason to watch the animated series. There's not really that much to like or enjoy about it, you don't know the proper background. Pokémon is grahpic wise and storywise mediocre at best. So it's not surprising if people prefer to watch Dragon Ball. Personally I think DBZ is a joke though, I liked the original DB much better.