I've always found it noticeably difficult to watch some of the old "classic" movies because I get distracted by the camerawork, storyline presentation (it WAS done differently back then), (by modern standards) sub-par special effects, lack of color, lack of movement etc. Generally I find that the oldest movies I can watch comfortably (regardless of how good the storyline is) are ones filmed within 10 years of the year I was born.
Many of my peers seem to feel the same way as well, as I've never had one of them pipe up with, "Hey, let's watch Bonnie & Clyde" when we're trying to select a movie to watch.
Not at all some of the greatest films ever made were filmed during in the early to mid 1900s. Casablanca is a great example arguably one of the greatest love stories ever filmed and it was filmed in 1942 using tech way older then I am. Another classic is it's a wonderful life.
I love seeing puppets and claymation in some older movies. But some of the REALLY old movies take some time to adjust to (for me) There are significantly fewer close ups and view changes in black and white movies. Most of the plots I just can't get into. Acting was more theatrical and less realistic back then too (look it up). Not to mention more sexist and racist. The action is never very dramatic, 'thrilling' scenes are boring (one scene I'm thinking of in particular is the plane crash scene from North by NorthWest), and don't even get me started on the romances! No one kisses another person by mashing their mouths together as hard as possible and then not moving for a few seconds. All the risque things like that (you couldn't really show 'making out' back then) that they couldn't show makes it less realistic. Like they're robots. I definitely understand the whole 'less is more' 'it was a different time' 'its the best they could do' 'its classic' stuff, but putting that sense of nostalgia behind movies now are just better. Of course there are exceptions, I LOVE the original Lord of the Flies, the Birds.. But nothing can beat an awesome action flick mixed with a modern sense of humor and some pop culture references with the most realistic graphics possible. Could you imagine a person from the 40's seeing a movie like Avatar? Or Transformers? Or Jurassic Park? It would blow their fucking mind.