not counting this one, the best YGO GBA game was Duel Monsters 6 Expert 2 (japanese, never released in the US), in my opinion. every one after that sucked, either due to missing important cards, having an atrocious AI, being boring as hell in the beginning, etc. a DM game in which opponents sacrifice their 1900 atk/4 star for a 1500 atk/5 star/no effect monster
(WHY IS THIS EVEN IN THEIR DECK?!) ceases to be fun or a challenge, because the AI has no idea what it's doing.
even duel monsters international/worldwide editon, which is basically a modified DM6, sucked. sometimes it's GOOD to let the computer cheat a bit, but the right way to do it is to sometimes give kaiba and yugi god-draw to complement their half-decent decks (OTK BEUD and Valkyrion/Black Magician, respectively). it really adds to the feeling to have kaiba kick your ass because oh look, he HAPPENED to draw devil franken, heavy storm, raigeki, duster, black hole, megamorph on his first turn. or yugi draws alpha, beta, gamma, valkyrion, valkyrion, raise dead, some magic/trap removal. ouch. i remember in a newer game, they cheated by allowing the computer to have multiple copies of restricted cards, but the AI otherwise sucked. BORING, especially since you can't do this yourself until ridiculously later.
this game better have awesome AI and such, as well as having every card that sees any use, plus of course those that don't (the sangenshin, preferably even the sangenma if they decided on their effects well enough in advance). but i guess they can leave the sangenma to a later game based on yugioh DM-GX.
