When I was around 11, Yu-Gi-Oh, or Duel Monsters for some, was one of the most lucrative, most popular trading card markets. I remember even attending local tournaments at Toys-R-Us. It was so main-stream in fact that niche shops like Gamestop and even 7-11's would stock booster packs in their inventories. Nine years is a long time for a trading card game to mature. The strange thing is that it is not just the rules and format of the cards that has grown with its audience, the anime has too.
Throughout each iteration of the anime, from the original Yu-Gi-Oh series, to GX, to 5d's, there's a noticeable shift in tone (I am disregarding zexal for the time being). Where GX is mostly a series categorized by school shenanigans and leisure dueling, 5d's is set in a dark and almost dystopian future. In a way, this kind of setting is probably the most appealing to me. The main-character Yusei Fudo is persecuted for his origins, locked in jail, tortured for information, and even blackmailed with his friends' lives on the line.
I want believe that this is Konami's way of nurturing its fan-base. At any local tournament these days, the majority of the players are 17-22, around my age. It is a true thrill seeing a community, that I was once part of, mature with the game and grow with the anime.