I always hated Cosmo's episodic running gags, Timmy's arrogance, the depressing negligence of his parents, and the irritating art style. I liked the show for about four seasons, then eventually said to myself "Why the hell am I watching this?" and stopped (around 2006)
I remember when this show originally premiered on Oh Yeah! Cartoons as a pilot, and I grew up with the series.
But the quality has drastically changed because...
1.They gave Cosmo and Wanda a baby, which apparently fairies do via males being pregnant instead. So thus most of the episodes tend to be centered around Poof, or Timmy having lost Poof or something... Which is strange considering older episodes when Cosmo and Wanda saw babies, they didn't care or give any knowledge/interest in having one themselves. What made them want one now? 1a. Now Timmy is getting a magical fairy dog as a pet [link] I mean.. he technically has 2 "fish" already. Wouldn't his parents be a BIT suspicious? Unless the dog is being completely hidden from them unlike Cosmo and Wanda in fish form. 1b. Overall a sign that an animated series is going downhill is when they begin to add new characters who frequently appear in future episodes (like every new episode mostly). The same happened with Nickelodeon's "Rugrats".
2. The characterization has definitely changed significantly. Like in older episodes Timmy would selflessly make wishes for his friends and even his parents because they were upset. Now in the newer episodes Timmy is portrayed as a selfish brat. Along with Mr. Crocker somewhat, because there is 1 episode where Poof becomes his "son" somehow, and he.. doesn't seem to acknowledge the crown he's wearing or anything.. what happened to being obsessed about catching a fairy? There's one in front of you!
3. This is probably more personal but, we hardly get to see any of the older characters from the show. What happened to Chester and AJ, his supposed "Best friends"? And one more thing, what about Vicky??? Considering Vicky's abusive babysitting is one of the main reasons Timmy got his fairies in the first place. Where is she?!