After breezing through this thread, I really need to check out Breaking Bad. Presently watching my wife's pick, Scandal. Actually pretty decent. All time favs:
The West Wing. Best everything, including strongest cast ever assembled.
The Wire, one of the only series to end as well as it started.
24, strong through season 4. Jumps the shark in 5 though and downgrades from great to good.
The Shield, best pilot ever. Although I suggest to pretend the show stops at season 4. 5-7 Goes from average to terrible.
Lost, Amazing through five seasons, then it jumps, literally to the ridiculous. Still angry at this show for killing off my two favorite characters.
The Sopranos, Love the cast here as well. Jumped the shark and ended at the same time.