I would recommend:

Fringe (as hullbg said it is slow to start and you think its just another x-files but stick with it and you will soon realise why its one of the most talked about show in the states, season 3 has took the show to a whole new level)
If your going to watch Heroes, just watch season 1, the rest are a big let down.
Supernatural
House
Dexter - highly recomend this one!!

The Event looks good, it has just started in the states and is soon to start on channel 4.

the one with jennifer morrison in it(dr cameron?).i was on a train with her to glasgow a few months back!!shared a cpl of drinks-i was smitten!!!

got every episode so far absolutely brilliant king of queens is another very funny one too.

Frasier

i have the lot!! my fav of all time!!

I bought the complete Lost box set the other week - 121 episodes and 30 hours of extras

I'm also a massive fan of 24. The final season is out on DVD in a couple of weeks so I'll be getting that to finish my collection.

I bought the complete box set of The West Wing a while back although I've never actually watched it, so I need to get into that soon.

Another highly recommended boxset is The Wire, which is just fantastic TV. I'm currently on season 3 of the 5, every episode I've seen so far has been brilliant.

The wire is superb (but I needed subtitles because of some of the slang/accents).

Comedy wise go for Still Game - absolutely brilliant!

Inbetweeners
Heroes (first series, starts to lose it's way by the third)
Scrubs
Torchwood (seriously, this show is boss)

Sopranos
Lost

Oh I've already seen it on Sky mate. I agree it was a fine season and back to form after a couple of shaky ones.

The Office
Extras
The Inbetweeners
Gavin and Stacey
Alan Partridge
Saxondale

Lost? The Wire and The West Wing I have had recommended to me off a lot of people although I've not seen any of them yet there ment to be good. I'm currently half way through watching series 2 of Dexter and so far its been brilliant, some great writing and the acting is pretty good from most of the characters to, there is currently 4 seasons out on dvd I think and the 5th season has just started in America tv fall. Another good show is Flashforward, althought it might be pointless watching as its only one season long and got cancelled, so most of the story lines were left unanswered. You can't go wrong with a bit of Friends either. Oh yeah and another good one is Early Doors, a comedy from about 5-10 years back but its pretty good.

Phoenix Nights.