I am probably in the super-minority, but I actually like Ariel's Grotto's food better than Storytellers Cafe, GK, and Plaza Inn (and I would rank them in that order, AG, ST, GK, then PI). I have never tried PCH Grill.
However, the character meals are not about the middling food quality (which all of them suffer from), but rather about which characters are important are important to you/your family. My DD2 is into princesses and Minnie, so we tend to go to AG and PI. However, the nice thing about GK, ST, and PCH is that you do not need entry into the parks to eat at at them--so, in the past, we have ate breakfast at GK and ST on the days we check out (we don't go to the parks on the day we check out).
EDIT:
Also, I have never had lunch at any of the above, only breakfast/brunch. And, to directly answer your question, I think AG is worth it if somebody in your party is into princesses. In my past experiences, their interaction with my DD2 has been wonderful.