There are three eras that separate the number of seasons for The Smurfs (1981).
Seasons 1-4 (pre-Smurflings era)
This season is considered the best by most Smurf fans because of its exciting adventures and dark atmosphere. Even when Baby Smurf came into the picture, he didn't take the spotlight away as much and had a few episodes of his own. Johan and Peewit had their own episodes too, but with the Smurfs shoehorned into the plot for each episode because the executives demand it. This was when the show was at its peak, before it was ruined to please focus test groups.
Season 5-8 (post-Smurflings era)
This is where the show started to decline gradually. Three Smurfs were de-aged into kids and a new female Smurfling joins the cast. Puppy is also added to appeal to the kids' demographic. To affect the change, Hanna-Barbera was forced to tone down the dark elements and made the conflicts sillier and more juvenile than truly frightening as before. Though this didn't stop them from having an occasional dark episode every now and then. The reception was pretty mixed (whether the new set of characters were a good addition or not), compared to the first four seasons of the show.
Season 9 (time travel era)
Best known as the steep decline of the show, where the basic premise was shifted to that of time traveling. Several fan favorites were eliminated and seventeen Smurfs were chosen to travel through several different time periods. This is what most Smurf fans consider as a "jump the shark" moment. The villains were replaced with descendant doppelgangers of themselves, referencing Biff Tannen from Back to the Future. At this point, fans lost interest in the show and was cancelled afterwards. The Smurfs soon disappeared from animation for a long time.














