I'm a HUGE fan of TV ON DVD & I collect so many different TV shows it's not even funny. I could probally recommend you alot of stuff but since you probally want to have some money in the bank I'll recommend you my top 10 picks:

1. Scrubs (comedy)
2. The Larry Sanders show (comedy)
3. Homicide: Life On The Street (crime-drama)
4. ER (medical-drama)
5. Boomtown (crime-drama)
6. NYPD: Blue (crime-drama)
7. Newsradio (comedy)
8. M*A*S*H (comedy-drama)
9. St. Elsewhere (medical-drama, witty banter)
10. King of Queens (comedy)

If you want more recommendations just ask!

Yeah, here is my top 10.

10.Arrested Development
09.Nip / Tuck
08.Rescue Me
07.Smallville
06.Buffy / Angel (Tie)
05.The Wire
04.Curb Your Enthusiasm
03.24 (Except Season 6)
02.The Shield
01.Six Feet Under

I agree with everything that has been posted. Here is a couple more

Coupling
CSI
How I met your mother
NCIS

These are some top notch shows to watch.
The Sopranos
Rome
Weeds
MASH
House
Deadwood

I am currently watching The Rockford Files season 2 with James Garner. EXCELLENT!!!

1: Veronica Mars

Others:

The Shield
Alias
Lost
Freaks & Geeks
Carnivale
24
Battlestar Galactica
Supernatural
Smallville
Family Guy
South Park
Futurama