If, like me, you want to truly appreciate the Simpsons, don't get Sky, stick with Channel 4.
We have to wait over 2 years for each "new for us" series, so then you anticipate and appreciate 100%.
As for the fact that the Simpsons is dead... no. If you are a true, you'll never think its dead. And as for past episodes, i've seen some over 100 times and the still make me laugh, and I will never not find them good or funny.
I find myself saying, several times a day, that I cannot wait for July to come, so that I can be about 32nd in line for The movie on July 27th, as well as a couple of HP related reasons.
And well.... Family Guy.... the less said about that show the better. "Plagerisimo".
In my opinion Family Guy will never, ever, ever even come close to being as good as the Simpsons, even crap like KTAAR.
And as for your other idea, well the only comparison is All Grown Up, which pretty much killed one of the best cartoons of its age, Rugrats. So I don't really think so. Matt Groening has said that he would like do 20 seasons, and will see after that. People will still watch whatever is produced so chances are it won't ever totally die, like Star Wars.
Role on 27th July!
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I pretend to know everything about The Simpsons, so if you have a question about it, I'll do my best to answer it.