Of course that was back in the days when I wasn't making my own salad dressings. Now, I still like Thousand Island, but I make my own. A friend gave me a recipe years ago that had a huge list of ingredients, but over time I pared it down to a more basic version. Thousand Island dressing doesn't need cheese...
However ... there are a few optional items that I don't always use, but that I like. Hard boiled eggs add a nice texture and thickness to the dressing, and the onions add ... onions. Neither are necessary, but they're nice, if you have them on hand.
Horseradish varies in strength, depending on the brand and how long you've had it. A teaspoon adds a nice zing if the horseradish is fresh. If yours is a little older, you might need to add a bit more to add the same amount of flavor.
Thousand Island Dressing
1/2 cup mayonnaise
1/4 cup chili sauce
1 tablespoon sweet pickle relish
1 teaspoon horseradish
1 hard-boiled egg, grated or very finely diced
1 tablespoon onion, finely diced
Combine all ingredients. Mix well. Taste and adjust seasonings as desired.