If I wanted to check out a certain show, I'd basically wait til the DVDs come out and pretend the last decent season was the last season.
I'm not into Family Guy and have no interest in watching it at all BUT, if I did want to watch it, I'd watch the stuff before it was cancelled the first time, when the characters were more sympathetic; The dumb but somewhat lovable dad, long-suffering wife, the evil mastermind baby, the voice-of-reason dog, the two teens.
There were only three REAL seasons of Spongebob Squarepants. The Spongebob movie was the finale. Anything after is not fully canonical. The creators even said so.
Likewise, with classic TV shows, for me All In The Family REALLY ended when Gloria & Mike moved away. The last season of Welcome Back Kotter never happened. M*A*S*H was best as a comedy.
I'm not into these movies but, to me, there were only 2 Alien films, one Planet of the Apes (Earth was never destroyed, Zira & Cornelius never went back in time & died, Zira & Cornelius birthing the whole ape planet thing makes my head explode & I'd like to think that Taylor & Nova became a new 'Adam & Eve', birthed kids, started humanity over with & vowed to do it right this time. The whole POTA saga is one big pessimistic bummer, IMHO), Halloween ended with Laurie killing Michel Myers once and for all in Halloween 2.0, etc.
There were also three Star Wars films (Ep. 4-6) & only two Poltergeist films.
And Metroid Other M never happened, no matter what that Sakamoto guy says! Samus is a strong, feminist badass heroine who's independent, not a needy bimbo in a cool supersuit who needs the "authorization" from some controlling jerk commander guy for everything & who questions nothing! The Samus/Adam relationship is like an emotionally controlling, manipulative domestic relationship.
Lets just say, I take "Canon/Fanon Discontinuity" very seriously. This is why I like the idea of fanfics, you can rewrite the story to your liking.