I've always thought that the wire was the BEST show on TV even if it is't my favorite. The acting and the writing are both phenomenal. The story arcs across seasons and across the whole series are satisfying while still completely plausible. And by most accounts, the microcosms of a city (the news media industry, public education, the drug trade, shipping ports, political bureaucracy, police department management) that are focused on in each season are represented very realistically.
That said (and I was disappointed to be the first to mention it) Trailer Park Boys is my favorite show ever. Many people just look at the title or watch the show for 15 minutes and mistake it for traditional american pseudo-reality trash about vulgarity for vulgarity's sake. TPB is anything but. The excellent job the actors do of appearing to be not acting (to clarify, good acting like in, say, The Wire or The Dark knight is very enjoyable to watch but is also instantly distinguishable from real life behavior) has fooled people I know into thinking it is an actual reality show. Underneath the brashness though, the real story is about a strong community and people who love each other unconditionally despite their handicap of being immature, reactionary, and ignorant. The show also approaches issues like unconventional family situations, sexuality, and animal rights with a nonchalance and subtlety you just don't see in American TV. I rewatch the whole series on roughly a monthly basis because whenever I have to spend more than 5 minutes picking a show, i usually just pick TPB. Everyone should watch it. Stepping off my soapbox now.
Starget SG-1 and Atlantis (I tend to lump them together because they follow the same continuity with many of the same characters, events, and locations) are also very near and dear to my heart. There is nothing quite like getting invested in a series and then having 15 long seasons to watch.