Any stew type thing is generally easy to scale up and usually follows the "better the next day" character. Goulash, curries, thick soups (beef barley is my favorite), and chillis.
There's no change in texture from reheating, which I think is key to good leftovers. Anything baked is going to dry out yet not be crisp, and anything fried is going to be soft and sad. Applying these principles to other things, and you come across things like lasagna as well.
For stuff that is baked, grilled, or pan fried, if it's something you can cook a bunch of, but pull most of it when it's 80% done, you can sometimes reheat that ok. We'll make 4 burgers out of a pound of meat, and either cook up 2 and just leave the other 2 for tomorrow, or say, pull 2 off when they're pretty rare, and cook the ones we're eating to medium. Then the next day, by the time the patties are heated through, they're to the right doneness.