For me, it would dffinetly be Yu-Gi-Oh.
As a 5 and 6 year old, one of my favorite things to do was sit and go through all of my Yu-Gi-Oh cards, simply admiring the art and descriptions of the monsters below their image, the descreptions were vauge enough so that I coul put together stories with each of them.
The art was the most amazing thing I had ever seen, so simple and so elegant, it was very diffirent from your typical anime, it had this majestic Medival European touch to it.
I would often draw up my own cards with their own stories, albiet the drawing part I wasn't so great at.
In a lot of ways, it was like my first RPG minus all the "OO MY CHARACTER HAS A DPS OUTPUT OF 112+889 AOE EVERY EIGHT MILLISECONDS!!!".
Call me what you will, but numbers and mathematics don't make or break RPGs for me.
Now a days, the art has evolved into just garbadge, and every card and their grandmother has an effect, the cards no longer had any emotion, they were just a mass of swords and gunswords with a funny sounding name.
Look at this, it is the first American generation of Yu-Gi-OH cards, http://www.toywiz.com/yugenlegofbl.html
And here is the most recent generation of cards, http://www.toywiz.com/hiddenarsenal3.html.
You should be able to tell the mass contrasts simply by looking at the names.
Aside from the actual cards, the early video games amazed me and still do, much more than pokemon or digimon ever did.
Now, if you feel the same way I do about this on some subject, post it here.
EDIT: Here is my favorite Yu-Gi-Oh videogame, http://www.gamespot.com/ps2/strategy/yugiohtheduelistsoftr/index.html
SECOND EDIT: If you wish to view the arts full progression, simply browse through them on the site provided.
