Colour TVs have been around so long that there are people who won't even watch Black and White movies no matter how much of a classic they are.
*raises hand*
Although it's not just the fact that they were B&W... IMO the acting in those days wasn't all that great. They were all so wooden; the so called greats of the era all spoke like they were either reading straight from the script or they all had 3 foot sticks up the butt. (Kinda like Keanu Reeves in other words. ) Not to mention that every male actor sounded nearly identical.
I try to judge movies, books etc by the standards of the time they were written. When older movies were done they were still evolving methods of acting and filming. The early films were using acting techniques designed for the stage without microphones, amplifiers or proper acoustic design. To judge them by modern standards is grossly unfair.
When you consider what they were working with some of the earlier films were brilliant and groundbreaking and deserve to be called classics for both their quality and the new techniques developed for them. Compare Forbidden Planet to the typical SciFi movie of the 1950's and Forbidden Planet is head and shoulders above them. Just like 1960's Star Trek raised the bar for Sci Fi TV shows and it was a long time before anyone raised the bar again.