Is it weird that my comfort films tend to be horror films, or dramas that deal with heavy subject matter in a cathartic way? I'll be honest: If I'm ill, I'm more likely to put on a zombie film than The Sound of Music (much as I love it). And if I've lost someone, I tend to find solace in films like Carrie, The Exorcist, Don't Look Now, The Babadook, etc. Or grief-themed dramas like Departures, The Tree of Life, and so on.
All that said, I do disappear into old episodes of Doctor Who and Star Trek for escapism. That's a bit more "normal" I guess. But for Back to the Future or Star Wars or Indiana Jones, I tend to only put those on if I'm in a good place. :)