As has been stated, the series are way too different to really garner a fair match up. Not to mention that you really can't match up the series in a clean timeline either since FF has way higher volume of titles.

I'd argue the original Legend of Zelda is better than all of the NES FF titles, but would turn around and say all three NES era FFs are better than Zelda II. Link to the Past is better than FFIV and V in my opinion, but not as strong as FFVI for me. Likewise, Link's Awakening is better than FFV but not FFIV. Ocarina of Time isn't as good as the four major FF titles released on the PS1, but I would concede that Majora's Mask is better than VII and VIII for me. Wind Waker is better than FFX and XI for me, but nowhere near as good as FFXII. Twilight Princess is better than any FF game released from the PS2 period onward. Skyward Sword isn't as good as any of them though. I have not played Breath of the Wild so I can't judge that one, and I'm unsure of where a lot of the handheld entries would fall though I would safely say that most FFs beat Phantom Hourglass and Spirit Tracks. I'm still debating on where I would place Link Between Worlds among the actual Zelda titles, so I couldn't even begin to figure out where it would land among the FFs, but going by its time frame, it's competing with XIII and I hate that game, but both titles have different standards as well.

Again, there is just different criteria for what makes both franchises appealing. If you only care about character and story then Zelda will almost always lose. Yet, if you're looking for a stronger gameplay that focuses on exploration and solving problems, then FF really doesn't hold a candle to Zelda. Zelda bosses tend to be more interesting and memorable due to a puzzle aspect to them, but FF bosses can be just as memorable for production values alone. The franchises are too different to make a fair choice and it really would come down to which style of game you prefer over which one is objectively better.