In a large bowl, whisk together mayonnaise, sour cream, Ranch seasoning and sugar. Gently stir in the corn, tomatoes, green onions and cheese. Cover and refrigerate until ready to serve.
Notes
Instead of regular canned corn, substitute with "Mexicorn" or "Fiesta Corn." These varieties include red and green bell peppers for extra color and flavor. Be aware, though, that the Mexicorn is often sold in smaller cans, so you need to make sure that you purchase enough cans to total approximately 30 ounces of corn.
Use fresh corn cut off the cob when it's in season. You'll need to steam or boil the corn for at least 3-4 minutes so that it's crisp-tender. Then drain it really well and let it cool to room temperature before adding to the dressing.
For a spicy corn dip, add some chopped jalapeno peppers, purchase a spicy version of Ro-Tel, or use Pepper Jack cheese instead of cheddar.
To make black bean and corn dip, substitute a can of rinsed and drained black beans for one of the cans of corn.
Serving a smaller family? Cut all of the ingredients in half to prepare a smaller bowl of dip. This recipe yields a lot!