Will do a shortlist if I get time, but the request is for sitcom not sitcomS. So if I was to pick just one it has to be the greatest ever combining cracking humour with genuine Shakespeare worthy drama and pathos it has to be:
Steptoe and Son.
Sublime in all regards. Two wonderful actors supremely cast so well it eclipsed anything either did or would do.
3rd Rock from the Sun Malcolm in the Middle That 70s Show Married with Children Will and Grace (if you call that sitcom) - except rather painful revival.