My picky eater likes some of the Michelina's frozen pasta dishes, I think because they are generally pretty mild in flavor. The white sauce ones go over pretty well, especially one that's got just pasta, cream sauce and a minute amount of broccoli (which she can skip if she tries). And they are inexpensive so it's not a big loss if your son doesn't like it. I suspect because they are less expensive, they don't use larger amounts of spices or pricer ingredients that can be polarizing for picky eaters.
In some ways, you might be better trying to find some other frozen pasta dishes he'll like, instead of trying to replace the homemade spaghetti and meatballs he loves. When my picky kid has an expectation of how something should taste, it's hard to accept something that's not the same - even if most people think it's good. But if you start with something familiar like a pasta, it might be OK to go with something new for the sauce.
Another thing you could try - is there a local restaurant the makes a spaghetti he likes? You could get an order for take out and divide it into smaller servings, since most orders are very generous. You could eat half and freeze half to heat in the MW later, or even divide into 1/3s. It might be slightly more expensive, but this dish is usually among the cheapest at most Italian places.