OMG! I finally got it! Yu-Gi-Oh! Ultimate Masters World Championship 2006. My hunting is now over since I have all the recent World Championship that I needed.
Here's my reason for getting them back.
YGO WC T 04 - Beta Test of the series. This game you don't really need unless you didn't know about the others or it was brand new, and you've bought the World Wide edition series for GBA.
YGO WC T 05 : 7 Trials to Glory! - Best game ever and brand new improvement of the previous WC. Also this game is as Similar as Nightmare Troubadour through its story mode; from then, KONAMI continues these stories Yu-Gi-Oh! game intertainment on the Tag Force series.
YGO WC 06: Ultimate Masters! - Best game ever! I finally realize that this game beats both DS WC in cards lol. The new cards are alright but who can forget Freed with RftDD or Wildheart Bazoo combos (Wildheart, Bazoo, Chiron, Giant Rat, and Exiled Force, RftDD) This game also has the complete set of Archfiends and the Sanctuary of the Sky sets. OMG, it has some cards that are from Japan and was never release to the US. Like the card shown from the anime Grendora the Dragon of Destructor!
BTW I don't have WC 04, and I never tried to get it lol. But If someone offers me it as a gift I'll take it