It's hard to critique this anime's storyline, not because it doesn't have one, which it does, but because throughout the five seasons, there are several different plots. However, the underlying story is that the Pharaoh Yami Yugi/Atem is trying to recover his memories.
Though it may take a little while in getting to explanations of what exactly is going on, the creators made sure to explain it through the characters.
I find the story interesting because it has links to Ancient Egypt--something that interests anyone, if only a little.
In the first season, the animation seems a bit old. Almost as if it were from the 80's. However as time passes and we get into the last four seasons, the animation improves dramatically. Though it could have still been better, the fluidity of each detail of every monster being destroyed and the flowing of water made it seem more realistic.
In the original Japanese version of the opening theme, the songs are almost perfect. In the English version, the theme always stays the same, almost in an annoying way. The sound effects were very realistic and the background music during an episode was always fitting for the situation. Whether it was soft music for times of relaxing or intense music for times of action, it always increased the experience of watching the anime to exciting heights.
One of the best things for an anime to do for its characters is to provide backstory on them. It really helps to relate to a character. Though we don't get much backstory and most of our characters, we get plenty of character development during the first season and the third seasons, the former being for "the gang" and the latter being for Seto and Mokuba Kaiba. I really liked the mixture of different personalities.
Overall, this is an enjoyable anime that may or may not pull at the heartstrings. We all love games and this anime combines, card games with adventure and fighting evil. It's the perfect anime if you want to watch rivalries between friends and foes, fighting evil, ancient mythology (Ancient Egypt, Atlantis), alter egos, and fighting monsters.
All I can say is by the time you reach the end, you'll be looking for more...
...and you will find it in GX and 5D's.