I'm with you on the cereal thing! Milk doesn't stay around our house long enough to finish it off, then the cereal is unappealing after sitting opened (resealed, of course, but not the same!) for a month!
Honestly, though, I don't eat breakfast 90% of the time. My stomach is weird, and I honestly get quesey and crampy if I eat too early, like before 10, or less than three hours after waking up, whichever comes first. So if I wake up at 10, I'm good for breakfast! But on work days, when I get up 6, I can't really eat until about 9. So maybe when I eat at 9 I have breakfast, but I usually just call it an early lunch!
Anyway, enough rambling, you asked a real question! Since cereal isn't so easy for me to eat, either, one of my favorite substitute breakfasts is eggs. I know some people worry about cholesterol, but they're really good for you. I like a hard boiled egg or two, sometimes with some salt. Simple and yummy! Or, simple rice. That's my Japanese heritage! Or a bagel with cream cheese. Or just bread, such as toast with jelly or a muffin.
Hope you find some good ideas here!