2011 Manga volume sales according to Oricon. The artist gets about ¥40-50 per volume sold.
1. One Piece - 37,996,373
2. Naruto - 6,874,840
3. Ao no Exorcist - 5,223,712
4. Fairy Tail - 4,701,596
5. Toriko - 4,665,634
6. Gintama - 4,415,491
7. Bakuman - 4,399,938
8. Bleach - 4,187,258
9. Kimi ni Todoke - 4,109,481
10. GANTZ - 4,056,981
Obviously, Dragon Ball beats One Piece especially on international sales. Everybody knows Dragon Ball! Your mom, dad, sis, bro, dog etc...
4kids already ruined One Piece

... But it is CURRENTLY the number 1 manga in Japan base on the sales ^.
Japan loves pirates than ninjas. Dragon Ball was so long a ago, it is legendary.
C'mon just look at the gap between One Piece and Naruto