Marril's two dollars (my thoughts are worth a hundred times anyone else's):
Magic, Pokémon, and possibly UFS (time will tell on this one) are the only TCGs out there with any kind of longevity to them that isn't tied in to some other aspect of the brand.
Yu-Gi-Oh is a lost cause, as has been said. The rules are poorly thought out and the cards themselves obviously don't get much (if any) playtesting. It's a brand built on a manga-turned-animé, and it shows. It did not survive the transition very well.
WoW, well, it's a crappy MMORPG and it's a worse TCG. I've seen it played, and it's very derivative of VS. The tie-ins to the MMORPG inflate the value of certain cards, but when all's said and done it has to rely solely on the name WoW has built for itself. If the name "World of Warcraft" was nothing more than a TCG, it wouldn't last more than a few months, tops.
Pokémon arguably relies on the video games or animé for its popularity, but when you have large swaths of players who loathe those other two brand aspects (sad as it is), it makes me think the TCG has some kind of appeal to it that goes beyond the brand name.
Its why in all the years in the U.S. not a single American has come close to winning Worlds of yugioh.
Bandit Keith did. In America.
And then a child beat him at a children's card game.
