Really I was even talking about back in the 90s or any time period, arguing about which was better is pretty much pointless because it really all depends on personal taste.
Like, you could argue about hardware or amount of games (Btw, keep in mind that the games SEGA published back then weren't all in-house, a lot of those like Vectorman, ToeJam & Earl, Ecco the Dolphin, Gunstar Heroes etc. were by third party developers. So games like those can't really be included when you're talking about the quantity of in-house developed games.), but at the end of the day it's all about which games you liked more. And seeing how different Nintendo's and SEGA's games were, it's pretty hard to compare them when it comes to quality.