Sticking to the OP rather than just 'old films I still like' my nomination is Mary Poppins.
I was captivated by the film on release, to the extent my mother had to calm a four-year-old Pale Rider for the benefit of other cinema goers.
Not wishing to spoil a fond memory, I didn't take up a couple of opportunities to watch the film as an adult until it popped up on Sky a year or so ago.
Still a very enjoyable watch, and an excellent effort by Disney to produce a film that appeals to literally all ages.
Looks like they've done it again, Mary Poppins Returns was only released in the US last month, and is already being touted as one of the best films of the year.
Strong cast, catchy songs, and from the look of a clip, they've kept the mixture of live actors and animation, which was groundbreaking at the time of the original film.
And there's even a cameo from Dick Van Dyke, although it seems Julie Andrews wanted to leave the way clear for the new lass.
https://en.wikipedia.org/wiki/Mary_Poppins_Returns