There is the recent The Fall Guy and the lightly older 21 Jump Street. (I liked both TV series but had no interest in seeing either movie.) Are there other examples? I do not mean comedy movies of comedy series, which are much more common.)
Starsky & Hutch
Land of the Lost was a kids’ show and had some silly stuff, but for what it was, it had a pretty serious tone. The movie version is pure goofiness.
Charlie’s Angels?
Dragnet with Tom Hanks and Dan Aykroyd.
Dark Shadows. The TV soap took itself more-or-less seriously most of the time, but Depp & Co. played the characters for laughs.
I haven’t seen the CHiPs movie (with Michael Pena and Dax Shepard) but judging from the trailer (red band trailer - NSFW) it went more for comedy than the tv series did.
I’m not sure about Baywatch. The show of course took itself seriously but the movie seems more self-aware.
If Wild Wild West wasn’t a comedy, it sure sucked. 
That’s a good example. I wonder if it’s the earliest one.
I don’t know how serious you would call the original A-Team but the 2010 movie is considered an action comedy. Ditto the 1998 film The Avengers although it failed at so many levels, who knows?
I think the TV show/movie I Spy contrast is more clear cut.
Let’s call the Depp Lone Ranger “inadvertantly funny”.
Yes, this list is alphabetical, why do you ask?
I feel that, if anything, the movie was attempting to be more of a straight action thriller than the tv series was.
I will note one reverse case:
“Seven Against the Sea” was a serious war drama tv-movie
As the name of the main character reveals, this became the comedy series McHale’s Navy
Was the tone of The Fall Guy really that much different? I watched it when I was a kid and remember it as being not very serious.
I’d consider it at least as serious as something like The Rockford Files.
Which, in turn, brings to mind how James Garner was up for a dramatic Emmy for the TV version of Maverick — which, of course, begat the big-screen comedy.
Emmy rules are simple: if the show is an hour long, it’s a drama, and if it’s half an hour long, it’s a comedy. Actual dramatic and/or comedic content is irrelevant.
All kidding aside, that was the year he was up against Richard Boone, who’d been nominated for headlining the half-hour drama Have Gun - Will Travel.
As lampooned by SNL:
I guess that’s why Adam-12 and Dragnet were so gut-bustingly hilarious.
(I can’t think of any hour-long comedies. But there must be some…)
The film Maverick was supposed to be a comedy? I guess I missed it.
The TV show always had a humorous undercurrent, I admit.