It's a tough time to be in the cereal business. General Mills, the biggest seller of cereal in the United States, announced another disappointing quarter Wednesday morning, marking the sixth straight time the company has reported lower sales.

Breakfast cereal just isn't the morning mainstay it once was, crowded out by other options like yogurt, snack bars and breakfast sandwiches. And families aren't sitting down to breakfast as often as they did before. Overall cereal sales are down six percent since their peak in 2009, and they're projected to continue falling through at least 2019.

But while there's been a gradual slowdown in the cereal aisle, some breakfast cereals are still pretty popular.

Take Cheerios, for instance. The cereal is starved for growth, but it's shown a remarkable resilience. General Mills, which makes Cheerios (along with a number of other popular morning carb-heavy meals), sold nearly $1 billion worth of the little circular guys last year, according to data from market research firm Euromonitor. While that's a tad lower than 2013 sales, that's still a hefty load of breakfast cereal. (Honey Nut Cheerios, for what it's worth, have been the best selling variety for years now, followed by regular Cheerios and Multi-Grain Cheerios).

Then there are a handful of cereals with higher sugar content that Americans still seem to love. Frosties, or Frosted Flakes, are the second-bestselling cereal in this country. Cinnamon Toast Crunch and Lucky Charms are also still popular.

Other cereals haven't fared so well over time, such as the once-coveted brand Wheaties. The breakfast of champions, which used to boast ad campaigns starring athletes like Michael Jordan, has been limping around lately. Last year, sales of Wheaties dipped to $17 million, per Euromonitor, marking at least the tenth straight year in which people bought fewer boxes of the the whole-grain flakes. Corn Pops, which managed only $88 million in sales in 2014, has also fallen out of favor.

See below for the full range of what cereals are doing well, and which ones are lagging.

Over the past decade, several shifts have taken shape atop the cereal world. Healthy cereals have, for the most part, bucked the downward trend. Muesli, the most resilient of the bunch, has been the only type of cereal to post consistent growth. Sales of the raw oat, grain, and fruit mixture have climbed in each of the past nine years. But Kashi, though it has struggled as of late, has posted considerable growth since the mid 2000s too.

When you look closer at the performance of each cereal over time, you can also see just how well sugary cereals like Cinnamon Toast Crunch, Lucky Charms and Froot Loops have done. The three have seen sales jump considerably (by 35 percent, 30 percent, and 17 percent, respectively) since 2005. And, perhaps more importantly, they have become more popular in recent years while other cereals have struggled.

"There's this odd dichotomy of people being very healthy at times, but then very indulgent at others," Justin Massa, the CEO of market research firm Food Genius, told CNN last year.

Some cereals, which aren't strongly associated with health or indulgence, have been left behind. Wheaties, again, has seen sales drop by nearly 80 percent over the past 10 years. Corn Pops sales have dipped by roughly 50 percent over that period. And Rice Krispies sales have contracted by 32 percent.

While some cereal brands have found a way to survive or even grow, there's still a lot of downward pressure on sales for one big reason. Busy American families pressed for time in the morning are looking for portable options, such as snack bars, that they can grab on their rush out the door. And the scene so often played out in cereal commercials — families gathered around a dining table, each person with a bowl of cereal and milk — isn't as common as it used to be.