It is Pokemon for me. I was a fan of the older games till they became repetitive and felt similar, but it captured me for a few years and was addictive initially. I've mostly played Nintendo's older games and the rest didn't capture me at all, though Mario Kart is fun.

Xenoblade.

I think it's kind of hard to argue anything but Mario, Zelda... and maybe an outside chance of Metroid. No other franchises have as many quality entries or advanced the industry as much as those.

Smash Bros

This is a tough choice... I want to say Zelda, but you really can't ignore Mario, especially if you consider the Mario IP as a whole, not just specific entries like the 2D and 3D Mario games.

So I'll consider it a tie between Mario and Zelda.

Xenoblade. So good that it got me back into Nintendo and video games in general

This is both difficult and easy for me. Difficult because Nintendo owns the plurality of all-time great franchises, but easy because I'm madly in love with Zelda.

Zelda's not only the best Nintendo franchise, it's the best franchise period. Over 30 years it's turned out masterpiece after masterpiece. Super Mario is a close second, and Metroid a comfortable third. Mario Kart and Donkey Kong are up there too.

Fire Emblem for me !

The Legend of Zelda.

Runner-up: Mario Kart.

The Legend of Zelda