Don't know why, but this idea has seized me, so I'm gonna go for it.
I've already got 23 titles and I've barely started thinking; winnowing this down to 20 for sixty years of televised comedy seems impossible. So, tentatively, the idea is to do a knockout for each decade, say 10 shows each, with the top two in each decade moving on to the final knockout. That'll give us 14 for the final round, which feels like a manageable number. I think I'd like to run the decade knockouts for a week -- I imagine a fairly clear 1-2 will emerge in that time, and if not, we can let it play out a bit longer. Then we'd run the final knockout to its conclusion.
Otherwise, I'll take my list and the suggestions here and cobble it down to something less sprawling and do a single knockout.
So throw out your thoughts for the format, and any suggestions for titles here. This will be open to American AND British comedy series, and not solely sitcoms.