They both have such a long line of classics but I always say Genesis has a bigger place in my heart just off the fact that I grew up with it. But when it comes down to it, I do legitimately prefer After Burner over Starfox, Columns over Tetris, Streets of Rage over Double Dragon and Shining Force I and II over Final Fantasy IV and VI. I don't think the Mario games felt as good or achieved as much as their NES forefathers whereas Sonic on the Genesis just felt like this intoxicating odyssey across multiple games of incredible landscapes and unforgettable soundtracks. Having Michael Jackson composing some of the music certainly helped as well.