Wht would you say is the best american sitcom?

It would probably be southpark but i think the likes of it and family guy shudnt be counted cos they dnt really follow a storyline throughtout each season. Scrubs was pretty awesome and freinds ofcourse. Scrubs was probably my favourite at the time and heroes was good. At the moment dexter is the best now or how i met your mother. Entourage is good as well. What is your opinion