I have never watched Lost myself. My wife absolutely loved it at first, but even she started to think it's gotten a bit silly recently and so she doesn't bother with it any more.
In terms of US shows personally I prefer things like Prison Break and Heroes. Outside of series like those I enjoy comedies such as Cheers and The Simpsons, and growing up I loved old classics like The A-Team and Knight Rider (both great shows when you're an impressionable kid, but you realize their foibles when you see them as an adult!)
UK-wise I love British Comedy - stuff like Monty Python, Blackadder, The Young Ones, and Bottom crack me up every time. I have also heard very good things about The Office, but amazingly have not got around to hiring out any DVDs of it yet.
I don't really like many Australian comedies. I think Aussies overall are very funny people, but unfortunately we write shit comedies. There are a few exceptions of course, the odd Aussie film is pretty funny, but there are no Aussie comedies or sitcoms which have stood the test of time like most of the stuff I mentioned above has.