The Sky Crawlers and Jin-Roh have very deep an intricate plots, drama, love, and of course talking. There are both great action scenes in both movies. Both movies are made by Production I.G., also, so they share a similar art style. (one little easter egg: there is actually a character in The Sky Crawlers named Jinroh)
Both made by Oshii Mamoru, same art style, same psychological pressure, same emotional depth, equally interesting plot twists, both a bit slow paced and in both a lot of air time dedicated to creating atmosphere of loneliness and desperate search of meaning.
Both set in a not-so-distant reality you don't know much how it came to be. You may enjoy the similar mechanical technology design, although Wonderful Days' sky theme is backgrounded. Both have very good art and music and well placed CGI, one important difference to mention is that while one is focused on developing the characters the other is in reaching the story's climax.
Even though Memories are divided into three parts, if you like the heavy atmosphere and slow enfolding plot of The Sky Crawlers, I think you'll like at least the first and third stories of Memories. Both shows explore the meaning of existence and identity, even though The Sky Crawlers is a more depressing overall and Memories is more psychological. I would say the first story in Memories about a woman's unflinching grip over the past and her love is similar to the girl in The Sky Crawlers, but the other stories in Memories are definitely worth watching too.
Both anime feature child pilots who fly aircraft during a war in alternate universes.
The Sky Crawlers is set in a world similar to ours with some differences. Simoun is set in a more fantasy-type world
In The Sky Crawlers, the pilots stay as children for as long as they live, while in Simoun, the pilots can choose when they want to become adults.
They both focus on drama and development, touching on philosophical and ethical issues related to the respective worlds that the characters of these two anime live in.
Both films consist of minimalistic plots and the characters act in an emotionally subdued way. Although they differ in subject they still might cater to the same audience because of their similar atmosphere. Both movies have good visuals combining traditional animation with computer generated imagery.
Both are extremely pretentious as far as the story goes, but somehow their animation and music forces you to sit through it. So maybe if you actually liked one of these, you'll also enjoy the other, considering I feel they have almost the exact same failures!