I've only seen the first four season (and I have NO desire to watch the newer ones). This was such a wonderful show! I wasn't a fan of season 3, but it was still good. Season 2 was my favorite, because it kept the season 1 characters and added great new ones! Season 4 was wonderfully different from the rest. It's also a shame the card game didn't take off like others did.
To those saying Pokemon is better, it's apples and oranges. The two shows have completely different premises.