Tv shows are crap as a format.
I don't watch any of these series... smallville, sopranos, entourage, 24 etc. Time consuming and non rewarding, in the end every tv show becomes stale, loses it's original cast or as in 90 % of the cases, they become lazy with the script. Dexter was fun for one season maybe.Prison Break. I got sick somewhere in the third season. The first season or seasons are always better than the inevitable "finale" which all series sort of speeds to.
Lost? Prison Break? Entourage has lost it's appeal as well, it's was the shit when it came out but with the long wait between seasons you expect something bigger and better but get the same rehashed jokes and characters after 6 months and it isn't as fun the second time around. TV shows are crap as a format and in it's form a show is rarely thought out have an ending, that's why the ending is never good. It's like a drug addiction, mindless numbing..
Comedy shows, on the other hand, are completely different. They don't pretend to have a thought out plot, they work because they just make fun of contemporary subjects so they can last through their writers humour and their casts age.
Family guy is good. how i met your mother and big bang theory are good but still they were better when fresh.
South park is an amazing show. i can't think of any other series who gets increasingly better and more brilliant after season 10(!!!)