I've always recommended people to do at least one character dining on their trips. It is a very fun but also relaxing way to meet with the characters without standing in line in the hot sun.
This is one such report on character dining at 3 different WDW restaurants: The Royal Table at Cinderella Castle in the Magic Kingdom, Chef Mickey's at The Contemporary Resort, and Play 'n Dine at the Hollywood & Vine in MGM Studios. While I agree that both Cindy's Royal Table and Chef Mickey are very popular, I don't think Play 'n Dine can be considered as such, at least from what I've heard (I haven't dine there while I've done both Cindy's Royal Table and Chef Mickey). In fact, I would think Crystal Palace and dinner at Liberty Tree Tavern might be even more popular.
While I also agree that the characters are the main attraction and not the food (thus, the food then to not be that good), I would say that the exception here might be Crystal Palace. The food there is surprisingly good! We have done both dinner and lunch, and the food was excellent both times.
So, if you want good food, and don't mind meeting Pooh and friends (and the noise level also tends to be higher), then I would truly recommend Crystal Palace. Just make sure you make advanced reservation.