Integration of tags and wish list
An alternative to the idea of allowing users to create their own lists.
I know you can create your own tags and view all of the tags you've created, but I feel like it makes more sense to combine this feature with your Wishlist. My vision is that there would be some sort of side bar including your Wishlist, followed by all of your tags (and perhaps the option to sort these tags in an order of your choosing).
That way you could have tags such as "Wishlist--Classics", "Wishlist--Top rated", "Wishlist--Foreign films", "Recommendations from Emi", "Favorite films", "Films for long flights", "Films with the best scores" etc.
*and as a side note, if you implemented some sort of recommendation feature, every film that my friend Emi (for instance) recommends could be automatically given the "Recommended by Emi" tag--perhaps with an intermediate "'accept' or 'reject' recommendation" step, haha.
Our tagging system is currently designed such that all tags are public, we might have to reimagine that decision if we were to overload tagging with ideas such as private-lists and recommendations. It would be nice to consolidate the lists ideas with the current tag features, though. We'll keep thinking about this going forward.