Preheat the oven to 375°F. Lightly grease a large oval baking dish or 2-quart casserole dish.
Beat the softened cream cheese and sour cream together in a large mixing bowl until smooth.
Stir in the corn, 1 cup cheddar, 1 cup pepper jack, the chopped jalapeños, most of the green onions, garlic powder, onion powder, salt, and black pepper. Spread the mixture evenly into the prepared baking dish.
Sprinkle the remaining ½ cup cheddar and ½ cup pepper jack over the top. Lightly press the jalapeño slices into the cheese.
Bake for 30 to 35 minutes, until the center is hot and the edges are bubbling. Broil for 1 to 2 minutes, watching closely, until the top is lightly browned .Let the dip rest for 5 minutes. Sprinkle with the remaining green onions and serve warm with tortilla chips.