Asklemmy

Where I live, the big 3 are mustard, ketchup, and mayonnaise.

If I had to limit it to the "big 3" you listed, I would have to go for mustard. There are so many different types and of the options listed, mustard is easily the healthiest (or can be the healthiest) since a basic mustard is going to be low in sodium, sugar, and fat while also containing healthy phytonutrients.

Mustard is also much more versatile than folks in my part of the world give it credit for. It seems like a cultural thing / learned behavior rather than based on actual taste preferences. For instance, a fairly bland yellow mustard actually goes well with french fries. A spicy mustard (the types that are almost like horseradish) goes well with a variety of roasted veggies like broccoli, brussels sprouts, cauliflower. Honey mustard works well with chicken in various forms. Lots of cheeses pair well with different types of mustard. I could go on, but I'll stop here.

Since the majority of folks are discussing condiments that aren't in your "big 3", I would say that my actual favorite condiment is hot sauce. I'm not a connoisseur by any means and I don't have refined tastes. I don't even like super spicy hot sauces. But I do use hot sauce of some type with almost every meal and I go through a lot more of that than mustard or ketchup. Granted, hot sauces tend to be high in sodium, so I try not to go overboard.