Roasting intensifies the corn's sweetness.
Heat a grill or broiler to medium hot. Brush corn with melted butter, and place on grill or under broiler, turning often, until about half the kernels are brown, 15 to 20 minutes. Remove corn from heat, and let cool. Using a sharp knife, cut kernels from cobs.
Combine corn kernels, tomatoes, onion, jalapeno, garlic, and cilantro in a medium bowl. Season to taste with lime juice, salt, and pepper. Serve.