I think most people who felt Part III was weak are people who don't like westerns very much. I remember as a kid, Part II was my favorite because of all the future-y stuff (hoverboard!), and Part III seemed kind of boring because I could just not get interested in that period. Later, I saw The Good, The Bad, And The Ugly, and realized there were actually westerns I liked, that it wasn't all just John Wayne movies or the cheesy ones that led to Marty dressing the way he did when he first arrived. Now that I've seen a lot more good westerns, Part III is almost my favorite of the series (though I still gotta give it to Part I).