Strong World is indeed one of the best One Piece movies out there, taking into account that there are a lot! (10 movies not counting the Specials, etc). The crew is all there, the story is fantastic and contributes to the TV series and the art/animation is seriously good!
What could I have asked more for? Well... maybe more elaborated fights, Zoro and Sanji fights were incredibly short and even Luffy Vs. Shiki was far from the best One Piece duels.