Well, if it's the smooth, creamy texture you're looking for, no natural cheese sauce that I've come across can substitute exactly for Velveeta. The taste of natural cheese sauce will taste more like cheese too. I have developed a preference for real cheese sauces and can't stomach Velveeta anymore, but it took a little adjusting.
This is how I make cheese sauce (for mac and cheese or veggies):
Melt 3 T. butter over med. heat. Stir in about 3 T. flour. Cook for a minute, but be careful not to burn. Wisk in 2 c. of milk. and 2-3 c. grated cheese (cheddar, jack, swiss, gruyere, any semi-hard cheese is fine or any combo). Adjust the thickness with milk. Season with salt and pepper.
This is how I make cheese sauce (for mac and cheese or veggies):
Melt 3 T. butter over med. heat. Stir in about 3 T. flour. Cook for a minute, but be careful not to burn. Wisk in 2 c. of milk. and 2-3 c. grated cheese (cheddar, jack, swiss, gruyere, any semi-hard cheese is fine or any combo). Adjust the thickness with milk. Season with salt and pepper.