
Ni no Kuni makes me wish Ghibli had done more games (the reason they didn't was a really bad Nausicaa game made during the 1980s that Miyazaki felt completely bastardized the movie). Valkyria has the Great War/Roaring Twenties flavoring of Porco Rosso.
On Ni no Kuni's battle system: It had a slight learning curve, but once I got past that, I actually really enjoyed it and found its battles better than the vast majority of RPGs I've seen. It's pretty fast-paced action and the battles are usually pretty brief. On boss battles you do have to watch the boss's body language so you can put your party into defense mode against a big attack.