Dying is easy, comedy is hard, so the saying goes — often quoted as a deathbed comment by Edmund Gwenn, but more likely spoken by Donald Wolfit during a discussion of acting.

So, we see a lot of convincing death in movies, from horror ("The Eye") to action ("Rambo") to supernatural farce ("Over My Dead Body").

But comedy — the kind that really makes you laugh — seems to be darn near impossible.

Every year, Hollywood — ever anxious to take advantage of any holiday (can Arbor Day flicks be far off?) — loads up movie theaters with romantic comedies in the weeks leading up to Feb. 14.

In fact, even though Valentine's Day landed on a Thursday this year, four movies opened that day. Although, oddly, only one of the four was a romantic comedy: "Definitely, Maybe." The other three were a science-fiction thriller, "Jumper"; a hip-hop musical, "Step Up 2: The Streets"; and an elaborate children's fantasy, "The Spiderwick Chronicles." Go figure.

But from mid-January through mid-February, we also saw the arrival of "27 Dresses," "Over Her Dead Body," "Welcome Home, Roscoe Jenkins" and "Fool's Gold."

And judging from those movies, cheap and cheesy sex gags still rank as the favorite comic devices of the 21st century, the chosen weapons from the arsenal of desperate filmmakers.

Maybe that old saying should be: Sex gags are easy, comedy is hard.

Cheap gags about sex garner easy laughs, which is why so many TV sitcoms start off fresh and smart and creative, but after a season or two settle for stale and smarmy and redundant.

And, of course, when something is successful, we see lots more. So thanks, "Knocked Up." Your box-office reign last summer ensures that sleazy comedy is here to stay.

Not that any of this is terribly surprising. Moviegoers who saw previews of the Valentine's shows listed here probably knew what to expect. There were sex gags aplenty in each trailer. (All of them rated PG-13.)

The one surprise might be the well-reviewed "Definitely, Maybe." The trailer makes this film appear to be as much a father-daughter comedy as a "romance" (a word apparently defined by Hollywood as "sex").

True, there were some distasteful lines in the "Definitely, Maybe" trailer, but one could be excused for thinking they might be fleeting. They're not.

In fact, at the packed-house screening we attended last weekend, my wife and I took note of several couples departing within the first 20 minutes.

The stupid sex jokes in "Definitely, Maybe" surround a newly divorced father telling his daughter about his love life with three women before she came along. We see all of this in flashbacks, which the little girl occasionally interrupts, and which are replete with sexual encounters and racy dialogue.

So this guy is telling his 9-year-old daughter all of this? Yeah, right.

But perhaps the idea that sex jokes are too easy is best addressed by a Mae West quote.

The iconic writer-actress is well known for many memorable one-liners, some of them racy but witty —"I used to be Snow White, but I drifted."

In the 1930s, when she wanted to translate her raunchy stage act to film, West had to censor some of the jokes. When asked about it, she said, "It's hard to be funny when you have to be clean."

These days it's hard to be funny even when you don't.

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