My understanding is that the 2600 is a difficult console to program for because of its limitations. I think the 16-bit consoles may be the easier ones to program for based on some comments I've seen people make. I'm not a programmer, so I can't speak from experience.
I know there is some form of Basic for the 2600, though, that makes it easier to program for the console. A new Basic is also available for the Intellivision.