I’m going to fall in the middle on this one. I recently played a few dozen Atari 2600 games, mostly from Atari and Activision, and many are quite good; good enough to rank alongside the NES/SMS greats. Titles like River Raid, Pitfall II, and Ice Hockey are playable and enjoyable today.
But in general the third gen is superior to the second. The NES, to use the best system of that era, enjoyed a lot of the replayable score-based games that featured prominently on 2600, e.g., Gradius, Donkey Kong, Jr., plus some longer, more in-depth adventures, e.g. The Legend of Zelda, Final Fantasy, and a whole lot in between, like Ninja Gaiden, Super Mario Bros., and Mega Man.