ABC (ended 2006)
Season One - Utterly groundbreaking. So good with continuity.
Season Two - Once again, faultless television. Probably some of the best in history.
Season Three - Interestingly different; breaking the mould a bit. Some strange ideas but very good.
Season Four - Without much footing for the first ten episodes, but after that, really very good. Shocking (in the positive sense).
Season Five - (unfairly cut short) First 5 or 6 episodes are just above good, just. The rest I feel is gripping, bar maybe a few instances. But after the 4 month hiatus, it rocked.