The Simpsons
In my humble opinion, The Simpsons is the best thing on television and since it has been running for 10 great seasons(another one coming up too) others seem to agree with me. Not only does the length of The Simpsons' run show that it is hugely popular but it also breaks the record for longest running prime time show, beating out ***. With the nth season The Simpsons overcame The Flintstones as the longest running animated series. Then throw in the record for most celebrity guest appearances and you have proof that Matt Groening and crew has a great thing going.
With "extremely crude" drawings The Simpsons debuted on The Tracy Ullman Show in 1987. They were just short clips that aired before a commercial break and the fan base starting building up. 
Then on December 17, 1989 the first full length episode ran and we meet Santa's Little Helper. Members of the original Tracy Ullman Show stayed on to refine their character voices and even expand it into the ever growing population of Springfield. Also with the vast array of different voices, writers can create new characters and find the right voice for it. All the different citizens of Springfield allow stories to emphasize someone besides the family once and a while and keep the show fresh.
Now here The Simpsons is well liked by many age groups and many countries. With celebrities calling to get themselves a spot on the show it doesn't look like it will be slowing down any time soon. Also The Simpsons enjoys taking pop culture and doing humor that only people in the know understand but now The Simpsons is defining pop culture on its own.