One great thing about food is that we all have different tastes and opinions. Our opinions are 100% right to us. Another example is that there are plenty of people who think that nasty deep-dish pizza one gets in Chicago is the best in the world, while others like the thin crust pizza we can find in NYC; personally I like the Greek-style pizza one finds in the Boston area.
What you say is quite true; I'm also guessing that some/all of the doubters in this thread haven't ever had an In-N-Out burger. While it is technically "fast food", an In-N-Out burger is nothing at all like the "burgers" one can purchase at typical fast-food places (McDonalds, Burger King, etc.).