According to Animaxis...

With "Yu-Gi-Oh" card sales exceeding 15,880,000,000 cards sold, Konami has contacted Guinness and applied for a card game sales world record.

I really enjoyed the first 27 episode series that was aired back in 1998 but, the later TV series "Duel Monsters" looked like it was turning into a Power Rangers sort of show with those devices on their arms. Didn't like it even though it followed the Manga series.

Source: Animaxis News
Related Links: Toei Yu-Gi-Oh Anime Site