Dennis the Menace (US): Dennis sure loves pizza, but hates vegetables of any kind with a passion... once to the point where he turns up the oven to 550 degrees on Thanksgiving Day, just so the family would be forced (in haste) to order pizza as their Thanksgiving dinner.
Eugene the Jeep: Orchids (Actually, that's the only thing Jeeps eat.)
Garfield and lasagna—the joke being that such a time-consuming and intricate meal is being served to a house cat.
The official Garfield website had an entire archive of lasagna recipes that fans had submitted for our favorite feline to enjoy.
In the earlier strips, Garfield used to absolutely love whole roasted chickens, until December 1980, when he never ate it again after Jon forbade it. Garfield then chowed down on hamburgers instead.
In the comic strip, one of his grandfathers explained why lasagna is Garfield's favorite food: as it turns out, the titular cat was born in the kitchen of an Italian restaurant, and when he was still a kitten, he accidentally tripped the cook as he was carrying a tray of lasagna and he had a bite (lasagna was the first food he ever ate). The animated half-hour special Garfield on the Town visually depicts this in a flashback.
While lasagna is still established as being Garfield's favorite food, it's rarely mentioned nowadays and, at least since 2006, seems to have been largely replaced by pizza (Garfield's favorite food after lasagna). Word of God seems to support this, as Jim Davis (the creator of Garfield) once admitted that he wishes he had made pizza Garfield's favorite, as he finds it a lot easier to draw than lasagna.
A Woolseyism example: In the 80's, one Norwegian translation made joika balls - a type of meatballs made partially from reindeer meat - Garfield's favorite instaed of lasagna. This required some Willing Suspension of Disbelief from the readers, since a plate of joika balls looks nothing like a plate of lasagna, but nevertheless the Norwegian Garfield fans regarded this as canon for years.
Calvin: Any sugared cereal, but particularly Chocolate-Frosted Sugar Bombs. He is also mentioned to like hamburgers, but is only shown eating them once. He's also been shown to go out of his way for pizza and cookies.
Snoopy of Peanuts likes cookies, and angel food cake with seven-minute frosting (and root beer, when he's in "Flying Ace" and "Joe Cool" modes). But his absolute favourite food is pizza. It's the only thing that could lure him out from under an icicle (he was afraid to make the slightest movement in case it fell on him).
An old Robotman and Monty (in its Robotman days) strip where Monty decides that he needs a trademark food, and spends much of the strip eating pork chops, before discovering that he doesn't really like pork chops that much.
Traditionally, Dagwood of Blondie has favored tall, multi-layered sandwiches (hence the term "Dagwood sandwich"), but in recent years he's expanded his palate to include stuff like pizza.
For a while it was stated that his favorite food was spare ribs with saurkraut.
Reversed with Mafalda and her mom's soup as her anti-favorite food. On the other hand, her brother Guille absolutely loves soup.
It's actually implied that Mafalda loves pancakes. The only thing that can convince her to eat soup is the premise of having sweet pancakes as dessert.
Raquel: Fine, if you don't eat your soup I won't give you dessert! Mafalda: I won't have it! Ever! And no blackmail can ever make me back off my principles! Raquel: ...Pancakes. Mafalda (gulping down the soup): Man do I squick myself so much at times!
At the end of every Nero album, the characters have an Every Episode Ending where they traditionally eat Belgian waffles. In real life, during special celebrations of the comic strip, waffles have been baked for the guests and visitors as well.
Banks of Barkeater Lake and bacon - to the point where he couldn't give it up even after having a hypertension-induced stroke.
Played with in a FoxTrot Sunday strip when Roger brings home a dozen doughnuts, and the kids immediately start fighting over the one with chocolate sprinkles. While they fight, Andy takes the chocolate sprinkled one — not to put an end to the fight, but because it's her favorite as well.
With Paige's sweet tooth, it's no surprise that her favorite treat is ice cream.
Opus the Penguin loves herring, with lots of mayonnaise. He also likes Ding-Dongs, Zingers, and similar snack cakes.
A basselope's favorite food is Pop Tarts. (This is also why the one in the strip is The Last of His Kind; they died out due to high blood pressure from clogged arteries because they ate them with too much butter.)
Rasmus Klump: The cast has at least one pancake dinner in every story.
Captain Haddock of Tintin loves Loch Lomond Whisky, until Prof. Calculus does something about it.
Rorschach of Watchmen is often seen eating sugar cubes, but given his personality, it's hard to know if he eats them out of like of the taste or simple need for something to give him energy easily. He also seems to be fond of raw eggs. And beans straight from the can.
He is never seen eating anything cooked (though he sits in the Gunga Diner). Probably because he thinks preparing food is a waste of time.
Breaker from G.I. Joe is constantly chewing gum. He's literally never seen without it and is willing to ignore direct orders to discard it.
All of the Dreadnoks are inordinately fond of grape soda and chocolate donuts. It's pretty much all they talk about, and sometimes the only thing they can ever agree on. Though if donuts are unavailable, chocolate anything else will do. Sometime after the fall of Cobra, Torch eventually went into the business of making the stuff himself with the wildly successful "Uncle Winkin's Hard Grape Soda Company". He probably did this solely to get it for free and just the way he likes it.
In Astérix, while roast wild boar is the staple diet of most of the Gauls, Obelix in particular obsesses over it. Being a Big Eater, he will have an entire boar, if not several.
Recent comics vary on whether Superman is a vegetarian or not, and if he is he prefers peanut butter and jelly sandwiches, possibly a shoutout to a licensed Superman peanut butter from the 1960s and 1970s.
Post-Crisis, he frequently mentioned that he liked his mom's rhubarb pie.
The two stupid rat creatures from Bone like their quiche, though they don't get it often (and one is in denial).
Deadpool likes chimichangas. Not so much eating them, mind you. He just enjoys saying "chimichanga". His real favorite food to eat appears to be tacos.
And according to the 2013 Deadpool, he "loves the smell of 372,844 pancakes in the morning"!
Uncle Scrooge's favorite food is stated to be lentils in Romano Scarpa's "The Lentils from Babylon." He manages to eat seven plates (six as part of a bet, over who would pay the check, between him and his nephews, and one more of the "Lentils from Babylon"), and appears to be willing to eat another six. He amazingly declares that he ate the latter for "marketing reasons", since the renowned lentils were actually mixed with linseed oil by the Beagle Boys, who, after packaging them at Duckburg (the linseed and their tampering with the ads ensuring that sales were kept low), bought them back at exceedingly low prices and, pricy export after pricy export from one country to another, cleaned them when they returned to Babylon, and so forth. Scrooge also seems to favor lettuce and tomato sandwiches, but that might be because they're cheap. It is also stated in other stories that 176-167 has a great fondness for prunes.
Scrooge's favorite drink is nutmeg tea.
Scrooge is actually a Big Eater in general. While his love of eating usually isn't seen because he's, well cheap, he does eat quit alot when someone else is footing the bill.
Batgirl Stephanie Brown seems to have a thing for waffles.
To the point where when her fans began a campaign for her return, they sent waffles and waffle mix. Reportedly, the DC offices are now tempted to make other unused characters fond of maple syrup, so they have something to put on the waffles.
Not to mention potato chips. He's rarely seen eating anything else. When Damian gets temporarily locked up in a room (supposedly used by Tim normally) after his arrival at Wayne Manor, an opened bag of potato chips can be seen close to the big screen TV.
Damian also appears to enjoy cereal.
Swedish comic character Bobo prefers to eat cucumbers.
Spider-Man's love of Aunt May's wheatcakes dates back to his first appearance in Amazing Fantasy. He's also fond of normal flapjacks, as well as pizza. And of course, New York hot dogs.
One Spider-Man Tangled Webs story that featured Tombstone as a Villain Protagonist shows his diet isn't very healthy (he is apprehended after suffering a heart attack) but the story also suggests that he's fond of corn bread.
Very subtly done with Laura Kinney, who doesn't have one particular favorite food, but favors anything that's spicy. When questioned on this preference by Gambit, she reveals it overlaps significantly with Comfort Food: She was allowed only very bland fare by the Facility, so eating spicy foods is a way to distance herself from her Dark and Troubled Past.
Desperate Dan from The Dandy loves "cow pie", which is a pie made out of an entire cow, with the horns and tail still sticking out. He also drinks something called "owl hoot juice".
Most other characters in The Beano and The Dandy are fond of large heaps of mashed potato with sausages stuck in it.
In Cerebus the Aardvark, Cerebus' love of raw potatoes comes up several times; he even yells at someone to "[...] leave the skin on! That's the best part! *CRUNCH*"
Sonic from Sonic the Comic loves fast food in general but is especially into bean burgers. The series dates to before chili dogs became his standard food of choice, though some fans still prefer bean burgers as they don't invoke Carnivore Confusion.
Roxy from Jem and the Holograms adores bagels and is usually seen eating one at least once an appearance.