Well, you know what the sages say: “When you’re tired of Quaker[sup]TM[/sup] Brand cereals, you’re tired of Life.”
We always have some variety of cheerios, usually honey-nut but not always. After that it is usually Frosted Flakes followed by Frosted Mini-Wheats followed by whatever was grabbed by whoever was doing the grocery shopping at the time, in terms of how often we have those cereals in the cupboard. About 50/50 on generic or name brand for any of them.
Special K
Bran Flakes - separately add Sun Maid raisins, much fresher
Shredded Wheat - the big original, no Jrs. or Minis
Rice Chex
Northfield, Minnesota has two colleges and a Malt-O-Meal plant. The students would walk outside and sniff “Oh, they’re cooking Tootie Fruities today!” (their version of Froot Loops, but comes in a bag at half the price)
They even had a Facebook group “My college smells better than yours!” And the cafeterias are full of all these generics.
Well, now that my daughter is all gradumicated, she misses her Marshmallow Mateys. When she does find them on the east coast, they’re in boxes instead of the proper el-cheapo bags. So I’m schlepping a couple of sacks of cheap Lucky Charms out to her.
(y’know, because the genuine General Mills fake marshmallows have way too much quality goin’ on…)
Grape nuts. My husband has grape nuts every day.
I go through phases. Right now I have a muesli and corn Chex. Corn checks are dull and sweet by themselves, but very good with berries and milk.
I’ve done Cheerios and wheat checks and puffed wheat in the past as regulars.
I enjoy lucky charms, but only buy them once or twice a year.
I rarely eat breakfast, but when I’m in the mood for cereal the only one I really like is Basic 4.
A layer of Grape Nuts under a layer of Raisin Bran. With rye toast. By the time I finish the Raisin Bran the Grape Nuts are edible. 
Also
Cheerios (any flavor)
Corn Flakes
Malt-O-Meal
Speaking of cereal, we were out of milk the other day, and I had a craving for my Special K with strawberries. But we did have cream. I put just enough in to kind of moisten it, and…OMG. I…I think I may never go back.
Grape-Nuts.
Cream of Wheat (not Malt-O-Meal).
I order a “bulk” size (25 lbs.) of low fat strawberry/ raspberry granola from Amazon and keep it in the freezer. I can’t find it in a smaller size.
I mix this granola 50/50 with Grape Nuts, with lots of seasonal fruit cut up on top, five days a week Monday through Friday.
About once a year I like cold cereal, so my go-to is Rice Krispies (Kellogg’s only, none of this store brand stuff) with a banananananana sliced on top, sprinkled with sugar, and ice cold milk.
Quisp - Which I have to get online, cause stores stink
Apple Jacks
Frosted Mini-Wheats
and Raisin Bran
when I lived on my own …fruity pebbles frosted flakes and froot loops
but I don’t eat them as cereal… I eat them out of the box by the handful like chips…
Fruit Loops.
I’m pretty sure no one answered plain Kellogg’s corn flakes.
Corn Flakes were heavily advertised during my childhood and very popular.
Beverly Hillbillies commercial for KCF
I never liked them. They get soggy very quickly in milk.
They must be in real trouble now. I don’t know of anybody that buys them.
Kroger bran flakes, which are surprisingly good, and vitamin fortified. Topped with some granola or walnuts, raspberries and banana.
Not sure why you’d think that. They might not be a top ten seller anymore, but they’re certainly pretty common, in my experience.
Store brand bite-size shredded wheat. No salt, no sugar. The only edible cold cereal. I’d go with the large biscuits, but there are in name-brand only, and cost twice as much.
Cheerios and some kind of Chex
Frosted Mini Wheats. Generally eaten dry out of the box.