I'd go with oatmeal, flavored to your liking of course.
Now before anyone tries to say oatmeal isn't a cereal, go look it up, it actually is...
Porridge is the original cereal! Crush or crack any grain, ideally fresh, and cook it just like oatmeal. Hot wheat porridge is pretty good! You can buy a hand crank device, called a "flaker" to crush your grains fresh for this (one brand is Komo). Oats this way have more flavor than that stale Quaker stuff, and whole grains keep fresh for years if stored properly.
Ham and eggs are so savory, I think I’d want something a little sweet. But it’d have to be a breakfast classic to match such an iconic pair, so I’d go with a bowl of cornflakes with sugar!
I haven't looked this up, but I maintain that Froot Loops (which are great) is really just "Lemon" flavored. But since people may balk at a lemon-centric breakfast cereal, they decided to market it as multi-fruit flavored.