Someone raised this question at Big Planet this week in response to my Top 40 Movies list, and since it might here as well, I'll go ahead and put my response here.
Short Answer
The head-on collision of over-the-top camp with anthemic rock and Technicolor visuals, sold with such enthusiasm and abandon, hit my 5-year-old brain like cinematic crack. And I'm still addicted.
Long Answer
Either the first or second movie we ever had on videotape, I watched FLASH so much growing up you'd have thought someone was paying me. The camp never registered then, the same way kids that age watching the Adam West BATMAN show thought it was completely straight. I took everything at face value. Flash and Dale meet Zarkov by crashing into his home right before taking off in his home-made rocket ship? OK. Flash holds off an alien police squad with football-shaped eggs and Heisman moves? Sure. And just what the hell was Mongo floating in: space, air, weird clouds? It didn't matter how long the head-scratchers list got, I never cared once I heard Max von Sydow say that great opening line, "Klytus, I'm bored. What plaything can you offer me today?"
FLASH actually has a lot going for it when you take the time to look. Although the two American leads, while visually well-cast, couldn't act their way out of a paper bag, the supporting cast hit the precise amount of over-acting their parts required to make them enjoyable and indelible to the viewer. Brian Blessed's maniacal turn as Vultan, King of the Hawk People always brings a smile to my face, just as Max von Sydow's Ming sends a chill down the spine. And how did they have Dr. Doom in the FANTASTIC FOUR movies not look like Peter Wyngarde's Klytus? Timothy Dalton shows some pre-Bond mettle, while Topol... well, I'm not sure what the hell he was thinking, but just go with it. The only thing more colorful than the Mingo sky was those who lived under it. And is watching Ornella Muti as Princess Aura really a bad way to spend a couple of hours? I think not.
As adaptations go, it's not the worst comic-to-film translation I've ever seen. For all those who decry FLASH as defiling a sci-fi classic, one read of the original strips (available from Checker Books) tells you it wasn't exactly high-brow entertainment to begin with. FLASH certainly didn't shy away from the 4-color palette of the original; if anything, it tried to be even MORE colorful. The designs seemed in line with the Alex Raymond art shown in the opening credit scene.
(* There's a very likely chance that I got into reading comics because of that art. Showing them linking the movie that I loved to comics, something I would seek out when I got a little older. The art itself was gorgeous, which certainly helped. One panel in particular had Flash standing on a mountain-top, hands on hips and surveying the land below. The way Raymond staged the panel, and drew Flash with his cape billowing around him, just said volumes about the scale and attitude of the strip. And as first impressions go, you can do a hell of a lot worse than Alex Raymond.)
And then there's the music. This movie introduced me to Queen, and I've been a devoted fan ever since. By this stage of their career, Queen had mastered not only the theatricality ("Bohemian Rhapsody" from A NIGHT AT THE OPERA) but the anthem-making ("We Will Rock You/We Are The Champions" from NEWS OF THE WORLD) required to do the film justice. Everybody makes fun of that title song, but that's because it did it's job. The movie's not called ATTACK FROM MONGO or THE WRATH OF MING, it's FLASH freakin' GORDON! That song and that opening tells you all you need to know: we're in some serious shit, and the only chance we've got is Flash, but don't worry because he's the man. All that with the catchy tune and Roger Taylor's thundering beat that gets your heart pumping just a little faster every time it comes on. Sure it's as subtle as a boot to the head, but who watches FLASH GORDON for subtlety? It's "Saviour of the Universe" time, baby! A subtle guy would have just shot Ming; Flash crashes Ming's own war-rocket into his wedding ceremony and skewers him on it. Subtlety, thy name is not FLASH.
So because I can trace not only my love for Queen but also comics back to it, as well as just putting a smile on my face every time I see it, FLASH GORDON is on my Top 40 Movies list.