These are all series that I would strongly suggest watching in their entirety:

30 Rock*
Arrested Development*
Better Off Ted
Black Books
Boardwalk Empire*
Bored to Death
Breaking Bad*
Californication*
Community
Dexter*
Eastbound & Down
Fringe
Green Wing
House
How I Met Your Mother*
It's Always Sunny In Philadelphia*
Justified
Mad Men*
Misfits*
Oz*
Peep Show*
The IT Crowd*
The Office*
Weeds*

The ones with a * are ones I'd consider a step above the rest, being long-running (either still on, or have ended), and that didn't take a major dive in quality at any point, and are worth sinking a considerable amount of time into. The rest are still great, but were either cancelled too early, turned pretty bad, or are just not quite as good.

Angry boys is funny,
V (2010) was pretty good.

Edit: my first double post

White Collar
Happy Days
Andy Griffith Show
Quantum Leap
Miami Vice
King of the Hill
Doctor Who
Frasier

Maybe I'll think of more later.

Can't believe I forgot SHERLOCK! It's a modernized version (yet very loyal to the source in its own way) by Steven Moffat and Mark Gatiss and it's brilliant! Six 90 minute episodes have aired so far. Not sure when the next series is coming 'round.

End of this year/early next year. So help me I shall figure out that twist before then.

you could watch the entire series of seinfeld, dragonball/z/gt, arrested development..etc..

NCIS is one of the best crime dramas in my opinion. It also adds a bit of comedy.

For comedy, I go with the Bundies or the Pythons.

Benidorm is really funny too

Buffy the Vampire Slayer
Angel
Firefly
Stargate SG-1(If you like it then Atlantis as well)
Stargate Universe(To hell with everyone I liked it more then modern BSG)
Trailer Park Boys(The greatest Canadian show)
Scrubs

Obviously My Little Pony: Friendship is Magic.
You should definately check out the modern Sherlock show, Supernatural, The Pacific or Band of Brothers if you haven't yet. Amazing series.

If you liked HBO's Rome (and wished with all your heart that they had the budget to do 5 seasons like they wanted to), you might like another historical miniseries. Rome was the spiritual successor to quite possibly the greatest miniseries of all time, I, Claudius. I, Claudius is a 1978 BBC miniseries about the first 4 emperors of Rome with all the intrigue, violence, and cleverness of HBOs Rome with better acting and no explicit six. It even features young Patrick Stewart and John Hurt. There are 12 (iirc) hour long episodes, so it's not too long or full-of-itself.

I think that needs some rewording.

the Gunn household is going through the series "Supernatural". In fact I just ordered the fifth season today

we watched "Ghost whisperer" not bad IMHO

I'm also personally watching the classic CG series "Reboot" with "The Definitive Mainframe Edition" (has all four seasons in one set)

The new show "The River" is pretty good. It's like a cross between Lost and Paranormal Activity.

Don't watch 'Homeland', it's pure fearmongering.


And it's crap.

I'm also biased.

We've got that already. Brilliant stuff.

If you haven't read the source material you should check out Suetonius' "The Twelve Caesars", ideally translated by Robert Graves, the author of "I Claudius" which was the inspiration for the series.

These are some great suggestions everyone.

Thanks.

Az

Doctor Who, but start with the first season.

Spartacus: Vengeance ?
South Park
The Simpsons
Criminal Minds
Bear Grylls: Born Survivor

House.
Firefly.
Star trek Enterprise.
Star Trek Original series, TNG, DS9 all are good.
Merlin is pretty good.

Yes and no. Band of Brothers is one of my favourite series ever, but I thought The Pacific was complete rubbish.

Yes! I, Claudius is amazing!

If you liked Blood and Sand, I'd check out Gods of the Arena as well. It's only six episodes if I recall correctly, but it's really good.

A man after my own heart.

Capital: You're probably right.

Walking Dead
Boardwalk Empire
True Blood
Spartacus: Gods of the Arena or Spartacus: Vengeance
Sherlock
Breaking Bad
Sons of Anarchy
The Pacific

In addition to a lot of the ones named before, some personal favourites :
Dead Like Me
Lie to Me
Life (not the BBC-show, but http://www.imdb.com/title/tt0874936/)
The Mentalist (only one that hasn't been cancelled yet.)