Hmm, I can understand your concerns a bit. Maybe you just need a little more time, for the last years to pass in memory, so that you can see the films without being influenced by their surroundings (media hype, topicality, up-to-date techniques or fashinable filmmaking, etc.,etc.). But I don't think that could be a problem with you, so I am at a loss to come uop with any logical explanation. 

If you are unable to compare recent films with older ones, maybe you should come up with a new rating/comparative system (I know I had to adjust several times during the last 9 years, as my opinion on what to expect from a film has changed so often). Or maybe it is simply that one cannot "objectively" compare many films from 2007 with movies made in 1931. It could be like comparing Picasso with Leonardo Da Vinci. They come from different times and have different priorities. 

But as I don't seem to have anything useful to say... this problem is a universal one. How do you compare things?