Commodore 64, sure, but I wouldn't recommend the Atari 2600 for beginners! I wrote a small game for the 2600 years ago, and it's a tricky little machine. It doesn't even have a video frame buffer, so you have to do things on the fly, depending on which line of the screen is being beamed (think of old-school CRTs).
Indeed, a whole book was written about it: https://en.wikipedia.org/wiki/Racing_the_Beam
The 2600 is fascinating and fun to code for, but for asm newbies I'd recommend the C64 or NES...