Most everything you need to know about the cereal can be found in this three-minute contemporary review...
The cereal only lasted about a year, but they managed to put out ten different sets of comics. (All of the box art can be viewed here, although they don't include the interior flap.) They apparently did realize that they would need to update the comics featured pretty often, but they still missed a fundamental problem which I haven't seen written up in any of the articles I found online while researching this. The problem Ralston missed is that you can read the eight comic strips on any given box in one sitting. The entertainment value they tried to instill in the box itself would last for all of five minutes. The next day, you're still stuck with those same eight comics. And the day after that, you've still got the same eight comics. And the day after that... until you finish the entire box of cereal. Which, if you followed the recommended serving size, would be about two weeks. One week if you had a sibling.
This was 1988, you'll recall, so people were still getting newspapers. If you were so inclined to read your funnies in the morning over breakfast, you'd not only get more frequent updates via the paper, but there were a lot more of them too. Even the dullest kid on the block could have figured out this issue after the second day with the box.
So even if you liked all the strips (and let's be honest, they weren't the cream of the crop back then, even if you're limiting yourself to King's properties) and even if you liked the cereal itself (and, by all accounts, that's highly unlikely) you've still got this fundamental flaw in the very concept. To get this to work... I honestly can't think of a way to get this to work. You'd almost need to make the box out of a digital display that updated itself daily. Which is technically do-able now, twenty years later, but our disposable culture hasn't gone so far yet that we can afford to put LCD screens tied to small microprocessors with a wireless connection into a shipping container that's designed to be thrown away after a week or two. It's technically possible, but insanely impractical.
I suspect the licensing of so many characters didn't help either. The problem most of those licensed type cereals had was that so much money was spent on the licensing that they had to cut costs on the food itself. So the cereal simply didn't taste very good. Batman cereal? Crap. Mr. T cereal? Crap. Smurf cereal? Crap. G.I.Joe cereal? Crap. (Flintstones is probably about the only one to buck that trend.) I've heard complaints that Morning Funnies was WAAAAY too sweet, but I just recall being generally unimpressed.
Morning Funnies is one of those weird, little footnotes in the history of comic strip lore, seemingly remembered more by cereal enthusiasts than comic strip fans.