Isn't this supposed to be a comedy?!

No. The main people I've seen that hate this film are just upset that it beat Pulp Fiction and Shawshank Redemption. So they make up a bunch of superfluous reasons for hating it like, "Forrest is too dumb!" and "Jenny was a horrible person." There's only one word to describe the haters of this movie. Trolls.

Green Goblin is great! https://www.youtube.com/watch?v=t1L4ZuaVvaw

"Here it seems clear that satirical humor was the intention and people don't get it!"

That was not the intention and we do get it. Sorry, you've completely misinterpreted and misunderstood the movie.

http://www.avclub.com/article/adapting-forrest-gump-turned-caustic-satire-sentim-242113

Is there a point where a film adaptation, by deviating too much from its source material, ceases to be an adaptation?

Consider The Curious Case Of Benjamin Button, the film of which retains only the basic conceit of F. Scott Fitzgerald’s original short story—a man who is born old and ages backwards. Everything else, including the vast majority of characters and incidents, are original to the screenplay, making it hard to view it as an adaptation in anything other than a technical way. (Writer Eric Roth was nominated for Best Adapted Screenplay for it, while Dustin Lance Black won Best Original Screenplay for Milk, demonstrating the confusing delineation the Oscars makes between being bound by historical record and very loosely bound to the merest trace of the original story.) It’s no secret that things will change when something is moved from one form of storytelling to another; it’s also pretty clear that Roth did not tell Fitzgerald’s story.

Button may be an extreme example, but consider another Roth script that made it down the red carpet: Forrest Gump. As he would again 15 years later, Roth kept the basic thrust of his source material—Winston Groom’s novel, in which a singular Southern man lives an eventful life in the 20th century, participating in key events and interacting with the key figures of the age (you can see why some viewed Button as a ripoff of Gump)—while inventing freely. The divergence from the source material isn’t as dramatic, in that many of the same characters and sequences occur, but the tone, aim, and much of the plot are completely different, so much so that it’s reasonable to ask: did Roth actually tell Groom’s story? Fans of the book must’ve been mighty perplexed walking out of Robert Zemeckis’ unlikely smash, having expected something subversive and getting something uplifting instead.

The key change that Roth made, according to Zemeckis in his DVD commentary track, was to zero in on the mostly one-sided love story that occurs between the title character—a mentally challenged man played, of course, by Tom Hanks—and Jenny Curran (Robin Wright). This was “the glue” of the picture, Zemeckis said. The romance “was the tone.”

But it’s not the tone of the book, which is something of a nasty piece of work, far more vulgar and cynical than the film. Groom’s Gump plays like a broader version of Being There, which also featured a slow man reaching great heights by virtue of his slowness; just as Being There’s Chance becomes a potential presidential candidate because people mistake his simplicity for profundity, so does Gump nearly get elected to the Senate on the strength of his slogan, “I got to pee.” (His advisers insist it “signifies frustration and impending relief.”)

So it’s a satire, although Groom’s target varies wildly and never goes too far—Gump’s campaign implodes when the press learns of his strange history, for example, meaning it isn’t a swipe against the smarts of the American voter. (The only clear stand the book takes is against Richard Nixon, who in his cameo tries to sell Forrest a fake watch). Sometimes the book feels like an economic polemic of the Upton Sinclair variety, with Gump as a blank-slate working man whose body is exploited for the army, for football and wrestling (where his costume is a diaper and his stage name is “the Dunce”), as “Spam in a can”—a non-piloting astronaut from the dawn of the Space Age. (Yes, in the book Gump is blasted into orbit, along with a boy monkey named Sue. Somehow the film—which has the character uncover Watergate, create the smiley face logo, and inadvertently pen the lyrics to John Lennon’s “Imagine”—is the more realistic of the two.)

But this idea doesn’t really hold because Gump is also presented as a chess savant and competent-enough business owner. His life isn’t dictated by luck or by his fundamental decency, as is the case for his cinematic equivalent (the book’s version isn’t especially decent), but by the guiding narrative principle of “one damned thing after another.” In a telling moment from the DVD commentary, Zemeckis reflects that producer Wendy Finerman read the book and saw an idea for a movie. “What it was,” he adds, “I don’t know.” (That Zemeckis, who was at the time known for commentaries on American society like Used Cars and Back To The Future, couldn’t find inspiration in the book is surprising in itself.)

Gump, truth be told, is not a very pleasant read, though it’s hard to view it outside the context of the film. (Like Goodfellas and Wiseguy, this is a case of a movie becoming so popular that it completely submerges its source material. The difference is, Goodfellas tells Wiseguy’s story exactly, only better, while the film version of Gump tells a different story. Neither source offers much to fans of the films.) Were some of Groom’s choices wrong, or do they just feel wrong in comparison to its far-more-familiar adaptation? Forrest’s mom is bitter and manipulative in the book; Sally Field plays her with boundless love and support. The book’s Lieutenant Dan is a thoughtful and philosophical man (who Gump doesn’t serve under, meaning he also doesn’t save Dan’s life), in sharp contrast to the Ron Kovic-esque figure played by Gary Sinise, who also feels more distinct for having an arc of finding peace. The film’s Jenny is a victim of abuse, which provides some texture to her wanderlust, bad relationships, and discontent (that the film creates this “motive” while judging her impulsiveness and the distance she keeps from Forrest is a mark against it). In the book the character is spacey and one-dimensional, sometimes on Forrest’s side, sometimes not, but never plausible as a lifelong romantic obsession.

I find it too much of a tearjerker to be a comedy.

Metallica, Iron Maiden, and My Little Pony: Friendship Is Magic fan

It's a comedy,a drama,a love story,and an action movie all rolled into one. That's what makes it so fantastic. You laugh,you cry,you cringe during the war scenes. You experience a catharsis -all the emotions of life through empathizing with a simple minded, lovable character.