I'll praise the value of Cage forever, only because of "Leaving In Las Vegas".
About the ending of "Broken Flowers" it was 100% Jarmush oriented, and the ideal for the movie.
SPOILER ALERT
It was satisfying, because it was in absolute balance with the whole movie (the trip of the character and his constant failures). Among others, the point of not finally finding his son, is that he learned to take his relationships more seriously, because he just realized their possible positive results (like having a son) that didn't even think about them before, also facts that were important to others, and not to him, that is why he abandoned all his ex girlfriends (or "made them" abandon him). He obviously still has the chance to become a parent again, but his whole experience made him regret for all his bad behavior in his previous relationships and taught him many things. Maybe there was not a son at all, but still it was a good lesson to learn.