In a large pot of boiling water, cook corn until tender, about 4 minutes. Cut off tip of each cob. Stand corn in a wide shallow bowl; using a sharp knife, slice downward to release kernels. To bowl, add tomatoes, avocados, onion, parsley, 2 tablespoons oil, lemon juice, 1 teaspoon salt, and teaspoon pepper; toss to combine.
Heat grill to medium-high. Clean and oil hot grates. Rub fish with 1 tablespoon oil; sprinkle with Creole seasoning and season with salt and pepper. Grill fish, skin side down, until skin is crisp, 4 to 5 minutes (if fish does not release easily, cook a bit longer). Using a thin spatula, flip fish and cook until slightly pink in center, about 4 minutes more, depending on thickness of fillet. Serve salmon with corn relish.
Be sure the grill is hot, and oil the grates well before cooking the fish -- this will prevent it from sticking.
This is a beautiful recipe. I made it in winter--so some amendments: 1) I cooked the salmon in a parchment envelope (used a large fillet cut, seal parchment, bake at 350 for about 25 minutes). Yum! Didn't have fresh corn, so I used kernels that were frozen and steamed to heat in bag (don't buy the kind in sauce). Made the recipe for my family and it was like eating heaven! Make this food!