The 5200 was released in 1982, built on 1979 technology. The Famicom was released in Japan in 1983 but didn't make it to the United States until 1986. If Atari had made better controller decisions with the 5200, and perhaps included 2600 compatibility, I think Nintendo would have had a much harder row to hoe when they came to the US.
Then again, if Atari had taken Nintendo's offer to distribute the NES in the US...
(Some people write speculative fiction about world wars having different outcomes. My "The Man in the High Castle" is to wonder about what the world would have been like if Jack Tramiel hadn't been forced out of Commodore, if the Amiga went to Atari, etc.)