Yeah, that was the true reason why they jumped the shark. I only went by what jumped the shark for me back then. Every year they seem to add a new character. 2nd season Johan & Peewit came around and I remember being like 'ugh' in the beginning each and everytime their cartoon came up. But then I manage to get use to them, especially seeing the Magic Flute movie. Now I love the two and wish that they were in this last movie more.
The thing about the Smurfs was, well... they were a one time thing in a Johan and Peewitt comic series. But they became hugely popular and they had spinoff comics of their own. So basically, the guest stars became more popular than the actual stars of the series. I give them nothing but credit in trying to give those characters part of the show, but it just wasn't the American appeal of the Smurfs. They might have used some actual Peyo comics at the beginning, but they just couldn't get the same Euro-comics feel into the show. At least in a way American audiences liked.
Foster's Home for Imaginary Friends. Again, I have to politely disagree. To me, the show still worked for awhile (again, mainly because of the characters themselves). I didn't see very many episodes from the last few seasons, so I can't really comment on the show 'jumping the shark' at any point. Although I do remember catching one of the TV movies (the one where Frankie goes to some imagniary book world), and found myself pretty bored by it.
Fosters is a special show. It's all about friendships and those sort of relationships. Plus, it's the most beautiful form of digital "Flash" style animation on television I've seen. Didn't see the last of the series, though... so I agree that i don't know where the drop off point is.
Meanwhile, I'm opposed to the whole "There's nothing in my taste on Cartoon Network, so everything is terrible on it" meme. That's said by some person that saw 3 minutes of an Adventure Time and 2 minutes of a Regular Show. On a bad day.
Look... anything animated on Cartoon Network is more welcome than stupid internet memes with their own show, crap movies you can see ANYWHERE else, and live action programming that's ripped off of Discovery Kids. And quite honestly, they hit a very high point recently. I still think they handled Chowder and Flapjack poorly, Symbiotic Titan was treated like garbage because no one wanted to make a toy line (like the all too well selling Secret Saturdays and Generation Rex toy lines that NO ONE can get rid of), and the fact it took them THIS long to find themselves after a million network head shifts after Mooninitegate is maddening.... but Regular Show, Mad, Adventure Time, DC Nation, and Gumball prove that the network FINALLY got back to somewhere recognizable.
besides... if CN still reran the old shows, we'd be complaining that they reran the same episodes over and over... if they brought back old shows, we'd complain that the writing isn't good enough. It's all about complaining that we're no longer little kids, isn't it?