Upgrading my movie collection to 4K: What are the first movies I need to upgrade?

In my entire library of movies I've ever only watched movies in full HD, and never considered upgrading to 4K. Until now!

I'm asking the community what movies I should consider upgrading to 4K first, before upgrading my entire library of movies.

To set the tone of the genres, here are a few of my all-time favourite movies:

  • The Lord of the Rings
  • The Matrix
  • Star Wars
  • Tron: Legacy

These movies will definitely get their 4K upgrade in due time, but I'd like to know what other movies, available in 4K at the moment, should I consider getting first.