Is Nintendo better than sega

Everyone has their own preferences. It's like the Android vs iOS of Mac vs PC thing. A company or product that survives isn't necessarily better. Think about VHS vs Betamax or Video 2000 (VHS survived and won, but was the worst of the three), or HD-DVD vs BluRay (HD-DVD was just as good, but failed commercially). Think about Sharp, who is a minor player, but makes the best LCD with their expensive Elite-series, and is known for making the most reliable tech. We perceive Sharp as a B-brand mostly, but in Japan, it's the brand with the national pride like Philips is in the Netherlands. Philips however doesn't have any real competition in the Netherlands, while Sharp does in Japan.

Lot's of great, innovative companies and product failed compared to inferior ones. So the corporate success isn't a proper measuring staff, unless you're talking about corporate survival. Not corporate success, because one can also talk about image, innovation, several subjective variables, etc.

In the 80s and 90s, Sega kids had as much pleasure from their consoles as the Nintendo kids did, and lot's of kids thought their system was the best, which was also the reason why they got it (or asked for it). The Dreamcast basically failed commercially, but is recognized as the greatest system from that generation by many.