Modern tools make for a remarkably smooth development experience, for a bunch of old-time platforms.

The NES, for example, has:

• Graphics editors which, though slightly quirky and buggy, are pretty straightforward to use, in full, high-res glory
• A functioning and reasonably non-buggy C compiler that you can use to write non-trivial programs without having to dwelve into assembly land too often (the game I’m working on now has about 10 KLoC and, not counting some libraries, only two hand-written routines).
• Several emulators, at least one of which (FCEUX) has an excellent debugger, with everything you might want from one – breakpoints, single-stepping etc.
• A wealth of in-depth documentation (see e.g. http://wiki.nesdev.com/w/index.php/Nesdev_Wiki )

Compared to everything I’ve heard about developing games in the 1980s, it’s amazing how easy we have it these days.