Magic: The Gathering underwent this, quite subtly for the most part until the major redesign. Compare cartoonish, coloured pencil works of the first few sets with the detailed paintings of modern cards and you will see that the overall quality has improved dramatically. This is mainly thanks to detailed art style guides of each of the new sets created.
Yu Gi Oh also has shifted since the beginning. The art is more detailed and less cartoony. For reference, compare Karakuri Spider with the other Karakuri.
Standard tabletop games
Dungeons & Dragons artwork has changed quite a lot since it was first released in 1974. The art has gotten steadily more Dungeon Punk, but this has let up somewhat in 4th Edition. A lot of fans of earlier editions do not like artwork from newer editions of D&D, and some fans of newer editions of D&D do not like the older artwork.
The artwork for Warhammer 40000 has changed almost as much as Dungeons and Dragons over the years, starting off with goofy, oversized scifi drawings not out of place in the first edition of ''Shadowrun and hewing steadily more and more toward Frazetta-style apocalyptic science fantasy. Most of the combatants received major redesigns along the way as well.
