Grave of the Fireflies is an amazing movie but very very sad. I was very moved by it.
Nausica is great romp as is Castle in the Sky. My Neighbour Toturo, Spirited Away and Princess Monoke are the most feted in the West. Howl's Moving Castke is beuatifully done. Kiki's Delivery Service is great and surprisingly rewatchable.
If you want a more adult film The Wind Rises is good.
Whisper in the Heart is for teenage girls and Ponyo, The Cat Returns and Pom Poko are ok but not top of the class.
Not watched any of the others yet