Here's my five cents on the subject. The original Legend of Zelda was a great game for its generation, and I think regardless what we may think about the game personally, the game deserves our respect for being the thing that kickstarted the franchise we love so much. But, gaming has changed a lot since the NES days, which is a good thing, because any artform/industry needs to grow and change as time progresses. It's inevitable that most games from the older days, no matter how revolutionary they were for their time, don't measure up to gaming today - and therefore will not garner the same kind of love it got upon its initial release.
I think people need to differentiate more between opinion and respect. There's nothing wrong about someone not liking a game, no matter how much you may personally love it. No one person is the holder of the objective truth, it's all subjective. What may hit all the right buttons with one gamer, may hit all the wrong ones with another gamer. But even if we don't like/enjoy a particular piece of entertainment, doesn't mean we don't value its contribution to the industry as a whole or how it may have influenced things that came after.
I personally have a lot of respect for the original Legend of Zelda, even if I do personally find it boring to play. Same way I have enormous respect for the shows, movies, books and music that influenced the things I love. Because without those pieces of entertainment, what I love today would never have been thought up and made. But no matter how much I owe any particular piece of entertainment for something else being made further down the line, doesn't mean I am obligated to like what came before. My personal taste is what it is, some things just doesn't appeal to me the way other things do. It's the same for everyone else out there.