Please. I watch 10X the movies you watch. On more recent films, I normally do full screen, and it keeps same aspect ratio. On older films, most often, aspect ratio changes make it look better. They were limited by the film, like the Edison format. When I watch foreign films, I even fix the subtitles, as sometimes they're pretty shaky, and it's obvious in many cases, e.g, they say "him" when they mean "her", there's misspellings, stuff like that. Plus, very often the timing of subtitles is off. That's a pain, e.g., I'm watching an East European or Russian film, and the subs are like 10 seconds off, but I can't seem to fix them. The story line, going from IMDB, sounds pretty good, but I can't get it right, as the subs come on before you even hear talking. Have to work on that one, called Brat.
I don't care what others say. I do what I want, but as mentioned, newer films much better sized, and I just fullscreen them. And you have no idea what aspect I'm downloading. It may be off and needs to be fixed. Black and white films can be pretty rough. Some of them need adjustments, and are poor copies. I watch some off the wall stuff. Ever see the "Pusher Trilogy"? Kim Bodnia is in one of them, Mads Mikkelsen in another(Mads plays Hannibal Lecter in the TV series. He was also the bad guy in Casino Royale(the new one). Mads is considered Denmark's best actor. Some of these need to be lightened, aspect ratio changed, subtitles fixed.
If you really want to go nuts on me, I watch foreign films at 1.20X the speed, so they're running 20% faster. Most of the time, anyway. As I can read the subs, it doesn't affect it at all. At 1.30x, they start to look like Charlie Chaplin movies, too hurried. Many foreign movie viewers do this. Poster Ben does this, as I met him in SC back a few years ago. You get to see more movies. I only speed up the foreign ones. I've seen 100 Scandinavian movies, episodes, etc. It's great watching them faster. Some of these are 20 episodes. It's like speed reading, as you are reading what they're saying.