Mix the spices. In a bowl, combine the chili powder, paprika, cayenne, and a pinch of salt. Heat the olive oil in a skillet over medium-high heat. Add the onion and cook until soft, 5 minutes. Add the corn, garlic, 1 teaspoon of the spice mix, and season with salt and pepper. Cook until the corn is softened, 5 minutes. Reduce the heat to low. Mix in the cream cheese until melted and creamy. Stir in the sour cream. Cook until warmed throughout. If desired, thin the dip with milk.In a separate skillet, melt the butter until golden. Mix in 3 teaspoons of the spice mix, plus a pinch of chili flakes and salt. Cook another minute, then remove from the heat. Mix the mayo and lime juice with a pinch of salt. Spoon the dip into a wide serving bowl. Top with grilled corn and drizzle the mayo and spicy butter over the corn. Sprinkle on the cheese and cilantro. Serve with lots of chips for scooping!