A bit of gravedigging on this thread, but I have two words to clear up the "is it or isn't it" question...
PHIL HARTMAN.
Think about it...Hartman was in other Atari 2600 commercials. Mostnotable is the ice hockey one where he acted fairly similar to this one. It looks FAR more like Phil Hartman than it does Bryan Cranston. And doesn't look anything like Cranston did in the early 80s.
there is absolutely no indication that it IS Cranston, other than some random person with a YouTube account first said to himself "Hmmm...that looks a little bit like Bryan Cranston" and posted a video, and typical of the internet, other people used that video as their source and then others used THOSE people as their sources.