Definitely Alias and Charmed :D
From my favourites!!

You can also choose Las Vegas or, if you're into sci-fi, a must-watch is X-Files :D

I would recommend Pushing Daisies or Las Vegas :)

EASSSSSSY you need to watch Buffy, Angel and Charmed! Three of the best cancelled shows out there and long ones at that!

If you like sci-fi, Firefly and Battlestar Galactica are two amazing shows (though BSG wasn't canceled, it just ended). I also really liked New Amsterdam while it lasted, which isn't a sci-fi. :)

From what you listed I've vote a go on Pushing Daisies! It was a really great show while it lasted!

Dempsey and Makepace :)

http://www.fanpop.com/spots/dempsey-and-makepeace

you can find more episodes to watch on this spot added from youtube :)

and of course X-Files :)

I would highly recommend Popular! It's an amazing show and incredibly dark & hilarious!

Is Say For You

Buffy The Vampire Slayer
Angel
Charmed
Alias

Amazing Shows That Are On For A Long Time.

Well,actually I recommend you Buffy The Vampire Slayer,Charmed and Related.
Related is about 4 sisters living in New York City

Ok so I am going to go by what you have listed and relay the tie in to you.
Based on you appreciation of Kyle XY, a great show that ended way to soon and when it was getting to the interesting parts. I would recommend Dark Angel starring Jessica Alba. It is a great show about a girl that has been genetically engeneered. She has cat DNA spliced to hers so she has super abilities. It is a little Sci-Fi and a lot of action. There is a mystery woven through the story.

Based on Friends I would go with Dead Like Me. It is about a girl who dies and becomes a Grim Reaper. Unlike what we know about them Reaping is a job and the story follows her and a group of reapers through their day to day life. I thought you might like this because it is a half hour comedy.

While it is still on the air House is really good. I thought of this because you are into Medical dramas, ie. Grey's Anatomy and Private Practice. Along with this I would go with ER as well, although I didn't personally like it. It had a 10 year run and loads of fans.

I am not sure where people came up with some of the shows mentioned but I will give you a list as well of some of my personal favorite cancelled shows.
Buffy The Vampire Slayer
Angel
Charmed
Firefly
Supernatural (this is it's last year)
Stargate SG-1 and Stargate Atlantis (these are great shows that I would recommend people to watch)

And lastly Alias is a wonderful show. It has romance, action, adventure, and comedy. Very good show that didn't last as long as I would have liked it.

PRIVILEGED, this show is perfect

privilaged is really good:)x

Buffy the Vampire Slayer - best show ever!
Angel - also very, very good
Alias - it's totally addicting! I've finished the entire 1st season in two days xD
Charmed - fun and ...magical ? ;)

and from non sci-fi:

That '70s Show - great sitcom with great characters
Samantha Who? - recently canceled. axed prematurely, but had a satisfying ending :D

Beverly Hills 90210;
That 70s Show;
Charmed.