I just had to join up, because I'm sick of Family Guy getting ripped on, and needed to vent about it. Matt Parker, and Trey Stone say that they think it's funny, but don't appreciate it's storyline. That it's nothing more than a bunch of random flashbacks that have nothing to do with the plot of the show. That is the plot. NO PLOT. It doesn't have to have a plot to be funny. It's called dry humor. This is what it really comes down to. Trey Parker, and Matt Stone are just pissed off that Family Guy has the balls to air things, that they're to afraid to play anymore, because Comedy Central might pull the plug on them. They've become a couple of pussies, just like Tom Green did. They started just like Family Guy, with crude, rude humor, and then cut their whole show down to a halfassed witty comedy, that's supposed to be giving us some kind of meaningless life lesson (that I don't give two shits about), so they don't get pulled and have to lose all their money. If I want a life lesson, I'll read the bible. They've become sell out's, and Seth MacFarlane is the punching bag now, cuz they have no balls left.

The other problem is, before Family Guy, South Park was the first show to challenge The Simpsons, and took probably over half of their viewers, and money. Then Family Guy came out, and took more than half of South Parks viewers, and money. And that's because Seth MacFarlane dares to go to places, that Matt and Trey would not even dare to go. They've become sell out's. They're the Metallica's of Comedy, and Family Guy is the Napster of comedy. Because they're to big of pussies to express themselves, without taking the chance of being pulled, they have to rip on Family Guy, because he doesn't care what anybody thinks. They're completely jealous. No two ways about it.

The dryness of Family Guy goes back to every classic comedy movie ever made. Monty Python and The Holy Grail, Airplane, Top Secret, UHF, Naked Gun, Blazing Saddles, Young Frankenstein, and so on, and so on. Those movies meant nothing. They were filled with countless slapstick jokes that were so dry, 70% of the world wouldn't get it. Basically the witless Pro South Park kind of croud. They don't get Family Guy, cuz it's too deep for their hollow brains to understand. It's actually a very intelligent show. South Park is nothing more than an on the surface cartoon, with tons of cussing, shitting everywhere, and has 3rd grade grammer, which every dead head skateboarder can get.

The so called legendary imaginationland episode from South Park was nothing but a poor attempt by Matt and Trey to show that they too can do flashbacks. It was supposed to be the ultimate flashback, including every caartoon character from the beginning of time, and was the most pathetic excuse for a family guy knockoff I've ever seen. Not funny at all. They need to lose the Larz Ulrich attitude, and realize that Seth is 3 times as smart, and witty as they'll ever be.           

Ok. I think I've figured it out. There's two parts to this answer, and I implore you to look at my analysys as a very logical explanation, and not just meaningless bashing banter.

South Park, and Family Guy both have the same sense of humor. Dry, sarcastic, and insulting. The underlying difference between the two, is that South Park tends to only go only as deep as ripping on current situations, as well as current political, religious, and hollywood charcters. Any half witted non conformist, that hates all the douche bag actors, as well as the fucked up world we're currently living in, can find humor in the bashings of all these things. They can do that easily, because they are only smart enough, and deep enough, to know what is currently going on, and have no knowledge of anything that has happened in the past. The main reason would be because the target audience for South Park is teen to late 20's. Now in this target audience, I would say this is either beacuse they're too ignorant, flunking out of school, or we're not brought up by older brothers, sisters, or family members, that educated them on all the events of the past. Passing down old albums, movies, etc., so they do not understand 80% of what Family Guy says, and people just don't welcome what they don't understand.

 Now I'm 35 years old, so the reason I can get family Guy so well, and find humor in most everything the show rips on, is because I know so much about our history. It's in a way, the Frasier of adult cartoon comedy. Not only do you have to be up on all events, and people of the current generation, but you have to also be just as smart on events dating all the way back to the beginning of time. Being this smart myself, 98% of everything said, and shown on family Guy, I can get, and I find moderately to very funny. You don't have to be very smart at all to find South park funny, becuase it's the world we're living in now, and it takes no brain power for us to get it.

The other part I believe that makes Family Guy so much more of a threat to viewers, is that when they are sitting in front of the tv with their companions, the depth that Faimly Guy takes it's jokes, makes everyone a target. 7 times out of 10, when Family Guy makes rips on someone in a flashback, or reference, we either know someone like that or have done it ourselves. In a way making us the butt end of their joke. 

Like for example, the two guys that are sitting in Starbucks writing on their laptops just so they can be seen. Do you know how many wannabe tools are sitting in Starbucks at any given time of the day, just so they can look cool, or smart while they're sipping on a triple chocolate mocha frappucciino, eating their Chicken Cordon Bleu Sandwich, on Ciabatta bread just to be seen. That's only one of several references Family Guy will make on all the mainstream mindless sheep following whatever trend is popular at this very second, only for that very reason. On South Park, we're laughing at other people, though sometimes the jokes on us, like the poeple who only drive hybrids, and smell their own farts, but Family Guy rips on SO many kinds of people that the joke is almost always at our own expense, and that pisses a lot of people off. Very few poeple are safe, when watching an episode of Family Guy.

Really I just think it's mainly because you have to be highly educated to understand Family Guy, and most people don't get the random popups throughout the show, because they're too mindless, and air headed to ever get it. It goes right over their heads. If they truly have a dry sense of humor, there's no way anyone cannot find humor in the jokes. Like when death takes Peter back in time, and he's at the bar talking to a chick, and that guy comes up with his collar sticking up to his scalp, like the Count off Sesame Street. What fucking tools. Everybody and they're brother wears their collars like that now because it's supposed to be cool, since it's on a mannequin at Hollister, but yet don't laugh when they see it on Family Guy. They're so dumb, they don't even know it was a style in the 80's. They're just straight up fucking stupid, is what I'm really trying to say. They couldn't point, counter-point with Brian off family Guy for more than a rebuttal sentence. It's just too smart, and witty of a show. And for that reason, all the ignorant, shallow, juvenile, on the surface, mainstream, wannebe kids, dressing, acting, and talking just like whoever, and whatever's cool at this very moment until tomorrow, will never get it.

-insert incredibly long reply here-

OP is either a crafty troll, or a pseudo intellectual mouth breather.  YOU DECIDE