Spongebob was good in seasons 1-3 and the movie. Season 4 had good and bad episodes. The good episodes in season 4 were Fear of a Krabby Patty, Shell of a Man, The Lost Mattress, Skill Crane, Dungeons and Dragons, Krusty Towers, and Best Frienemies. The bad episodes were Good Neighbors, Funny Pants, Karate Island, All That Glitters, The Thing, Squid Wood, and Best Day Ever. The rest were meh. Season 4 was mediocre. Seasons 5-8, I can't stand the show. It was just bad.
Spongebob: Used to be a happy sponge that likes work and was only a little annoying. Now, he sounds like he is hyper on sugar and is really annoying.
Patrick: The starfish who was dumb and hallourious. Now, he is really dumb and annoying.
Sandy: The squirrel who lives under water and used to do karate. Now, she is obsessed with science and is a bland character now.
Squidward: The squid who hates Spongebob and Patrick and is never happy. he hasn't changed at all, only he gets tortured now, and that isn't funny.
Mr. Krabs: The greedy crab who had a heart. Now, he has no heart, he is more greedy, and he is a criminal.
Plankton: The plankton who always tries to still the krabby patty formula. He hasn't changed either.