I'd agree with most of the dissenters here that the vast majority of shows being mentioned are personal favorites (which is fine) as opposed to BEST television shows of ALL time.
IMO, the criteria to be considered the 'best' would either be shows that were universally popular and stand the test of time (ie. "I Love Lucy" and "Seinfeld") or, better yet, were groundbreaking in some way.
To the latter I would include "All in the Family", for dealing with a multitude of issues for the first time on TV (racism, miscarriage, rape, etc), and "M*A*S*H" for a lot of innovative style and risks (full episode of a patient's first-person view, mock newsreel, no laugh track in operating room, showing blood, etc)- both of which were also very popular ratings-wise.
My 2 cents.