The longest running show ever is "The Simpsons" with 31 seasons. It is an American animated television sitcom created by Matt Groening for the Fox Broadcasting Company.
Apart from that, other TV shows with long seasons include "Grey's Anatomy" (15 seasons and counting), "NCIS" (16 seasons and counting), "Law & Order: Special Victims Unit" (21 seasons and counting) and "South Park" (23 seasons and counting).
Other shows with long seasons include "The Walking Dead" (10 seasons and counting), "Supernatural" (15 seasons and counting), "Friends" (10 seasons), "ER" (15 seasons), "The X-Files" (11 seasons) and "Modern Family" (11 seasons).
If you're looking for an animated show with high seasons, apart from "The Simpsons," you could also check out the cult classic anime "One Piece," which has had 20 seasons so far.
Overall, the longest running show with the highest number of seasons is still "The Simpsons," followed by "Grey's Anatomy," "NCIS," "Law & Order: Special Victims Unit" and "South Park."