Conquest. I once read that there's a 'rumor' about a sequel of it(it's on Japanese but looking at the article I could assume that).
I also played the first PMD series, but I couldn't pass through Moltres. Still a pretty good game though.
Give Explorers of Sky a try, they refined everything so it should be easier (remember to make use of throwable items and consumables) and the story while seemingly childish at the start is actually really really good and well done.
Managed to play it early but the ROM hates the save mechanics >_> --- Official Nozomi and Trumpeter of the SMT4 board. The sole rule of any videogamer is to save save save. Especially when something rare happens. - LightHawKnight