Hard to say... Both of them constantly battle for my heart to be recognized as my favorite console ever... Or some other metaphor that sound better...
Anyway... I'm inclined to go with the NES, because I consider it more innovative and relevant overall. I believe most of what the SNES did was just expand the concepts introduced before, a big part of it due to the technical limits of previous platforms. Of course, you could argue that the NES also took many things from the Arcades and some from other platforms, but I think the NES concepts tended to be modified for the platform because of its hardware limits, while the SNES got more faithful ports. Like how Ninja Gaiden, Bucky O'Hare and Teenage Mutant Ninja Turtles got to the NES compared to Street Fighter, Final Fight and, again, Teenage Mutant Ninja Turtles on SNES. Just a tendency though, as you can find some examples of the opposite.
The SNES lineup is probably the more diverse, but there were clearly some genres taking precedence over others, so not every genre got meaningfully expanded to me. Notably, the RPG genre had a major boost, given how the new technology allowed stories to be more visual and impactful. On the other hand, I wasn't as satisfied as with the NES in regards to platformers and some other action games. What Capcom, Konami and Nintendo did in this area was more relevant to me in the NES era in general, with some of the best SNES games just doing what was done before in a more polished way, most of the time with older IPs. And I missed my Ninja Gaiden !!
Sure, the fact that the NES was the first console I've owned might have an effect on the way I see things today... But hey, everyone is biased in some way. I guess I should mention though that my favorite SNES game slightly edges out my favorite NES one (Chrono Trigger and Super Mario Bros 3). Ask me tomorrow though and I might have a different opinion...
