I’ll throw in a few morre:
“Sunshine Cleaning”
“You Can Count on Me”, with Laura Linney"
“Gaby: A True Story” – this was better than “My Left Foot”, same year, similar story line.
Funny Face, with Fred Astaire and Audrey Hepburn.
Chocolate, with the too-gorgeous-to-be-real Juliette Binoche and Johnny Depp.
The original theatrical McHale’s Navy, with the TV cast and Claudine “I didn’t mean to shoot him, honest!” Longet.
The original theatrical Batman, with the TV cast and Lee Meriwether filling in for Julie Newmar. :o
This is my all-time favorite movie, but I didn’t suggest it, because it’s slightly dark.
Excellent movies. Not in the slightest bit light or funny. Gaslight is a particular favorite, and I highly recommend it, but, definitely not light.
Anything by Bill Forsyth (Local Hero), especially That Sinking Feeling. Witness for the Prosecution will have you on the edge of your seat, but, not light-hearted.
Those Magnificent Men in Their Flying Machines, with Benny Hill (yes, Benny Hill!), lots of vintage aircraft, and the uberhot Sarah Miles. :o
Chocolat with Juliette Binoche, Judy Dench, Alfred Molina Johnny Depp.
Paris, je t’aime 18 short stories with different cast and directors
Hot Millions, with Peter Ustinov, Karl Maulden, Bob Newhart, and “Oh, God, YES!!!” Maggie Smith. :o Probably the first movie to feature computer crime, this picture was years ahead of its time!
Never Steal Anything Small, with Jimmy Cagney, Roger Smith, and yummy Shirley Jones.
Bedtime Story, with David Niven, Marlon Brando, and still-yummy Shirley Jones. Later remade as Dirty Rotten Scoundrels, with Michael Caine, Steve Martin, and the tempting Glenne Headly.
The Man Who Would Be King, with the great Sean Connery, Christopher Plummer, and Michael Caine. Kipling was never better!
A Shot in the Dark, with Peter Sellers, Herbert Lom, and “Do me next, PLEASE!” Elke Sommer. Arguably the best of the Inspector Clouseau movies.
Yankee Doodle Dandy, with Jimmy Cagney as the great George M Cohan. You’ll love the part where he tap-dances out of the White House and into a parade with the Army of the Potomac!
This Is the Army, with Ronald You-Know-Who and a cast of thousands (all in uniform)!
Lady and the Tramp, my second favorite Disney movie. (You *do *know why all those male dogs are chasing her, *don’t *you? 
)
Any of the Wallace and Gromit movies, especially ***The Wrong Trousers ***and The Curse of the Were-Rabbit.
The original The Parent Trap, with Hayley Mills playing the twins. Far superior to the “Easy” Lindsay Lohan remake, IMHO. Hayley’s singing is worth the price of admission all by itself.
The Castaways, also with Hayley Mills. Her first movie, Tiger Bay, in which she plays opposite her father John Mills, is a great picture but not exactly light. (Though I suspect you’ll shed a sentimental tear at the end.)
Pollyanna, again with Hayley Mills. She was everywhere in the early '60s. :o
The Station Agent is light hearted and mature. There are some heartfelt sad moments, but the situation and the characters keep it moving. When it’s over you’ll be glad you saw it.
I agree with the poster above, it would narrow our focus if we knew which platforms the OP has. ‘ALL MOVIES with these broad characteristics’ is a lot.
Already been done:
Going to think of some obscure ones here and there that most people missed. Start with:
Ed and His Dead Mother. It’s like it says on the box. Would violate the OP’s “not stupid/juvenile” rule except that Steve Buscemi’s character lifts it up into something else. The sad sack with hope is perfect for him.
(Raising Arizona and The Big Lebowski haven’t been mentioned. Maybe pushing the envelope, OP-wise.)
Harold and Maude. Bizarre, but light.
Sirens – the 1994 one with Hugh Grant, Tara Fitzgerals, Sam Neill, Elle McPherson, Portia diRossi, etc. Gorgeous cinematography, quite a lot of non-gratuitous nudity, plenty of humor, lovely costuming and great dialogue, seriously, this is the movie I watch whenever I’m feeling blue and need to cheer up.
Ooo, good ideas. My personal W&G favorites are The Wrong Trousers and A Close Shave.
Wow, I just watched this in the past month. The brother is a little hard to take, but everyone else is enjoyable. Better than you’d think it could be. Plus bonus Stevie Ray Vaughan & Dick Dale.
I just watched ***Bull Durham ***- the story of a rookie pitcher and the veteran catcher assigned to show him the ropes. Kevin Costner, Susan Sarandon, Tim Robbins, and an enjoyable supporting cast. Fun and funny.
You left out Bob Denver:
“You know, I lived with a guy for years. A real genius. He could take a couple of these pineapples or a couple of coconuts with some strings and wire and make a nuclear reactor. But he couldn’t fix a two-foot hole in a boat.”
Hair directed by Milos Foreman.
Englishman who went up a hill and came down a mountain. Hugh Grant stars.
also Waking Ned
Hugo, an absolute masterpiece by Martin Scorsese:
Some recent, critically acclaimed, feel-good movies from the past couple of years that I enjoyed. None of them are really comedies but they are light dramas with ample humor.
Brooklyn
Nebraska
Hidden Figures
The Martian