I feel that the older films had a stronger focus on characterization with special effects used to enhance the story. I feel that this has been lost in the recent films.
I think that sometimes having a small budget forces people to make decisions judiciously. For instance, I was watching Mr. Plinkett's review of the Star Wars prequels. He mentioned that the people who made the original films had to be careful with the light saber effects due to the costs involved with each battle. This kind of constraint forces writers to be creative. Now, with CGI and larger budgets, a film maker can have as many light saber battles as they went, even when the battles don't enhance the story. Now, films I feel are bloated by this excess.
I liked the original "Andromeda Strain" and the "Flight of the Phoenix".