Activision is a very doable set right now but will probably get much harder later on. I'm missing double dragon too along with beamrider, decathlon and maybe another one can't remember.
If you collect alot of 2600 boxed games it's amazing seeing the variation in colors on the shelf.
Yes, it's definitely doable, but the prices continue to go up. Games like Beamrider, Cosmic Commuter, Private Eye and Hero show no signs of slowing down, either. Double Dragon has been almost impossible for me to obtain boxed due to price. While I was at the National Videogame Museum in Frisco, TX a couple of weeks back, I also saw there was a Gostbusters 2 for the 2600 and I had no idea that even existed.
I'm big on Activision and the color/gatefold Atari 2600 games..those were the heavy-hitters of my youth with the Silver box games coming in a close second, so I'll have a special spot in my heart for all of them for the rest of my life.