I would say live dead from 1977 is my favorite a lot of my favorite songs made their debut that year.
My older brother was a big deadhead in the 80's so I got used to have a lot of bootleg tapes. Then I got into Phish and left the dead behind. Now that I'm getting a bit older I do like going back to listen to older Dead shows,
I really like going on to Llama to either download shows or to stream shows, http://www.archive.org/browse.php?collection=etree&field=%2Fmetadata%2Fcreator
there are a total of 2,872 live archived GD shows on there and a ton of other great bands
I really like the New Years Eve run from 1990 that was the time when Bruce Hornsbey was playing keyboards for them and Brandford Marsilis sat in w/ the dead for some awesome stuff.
Also a good show
Grateful Dead 03/29/90
Nassau Coliseum, Uniondale, NY Branford sits on the entire second set and it is incredible. Eyes Of The World-> Estimated Prophet-> Dark Star-> Drums-> Dark Star-> The Wheel-> Throwing Stones-> Turn On Your Love Light, E: Knockin' On Heaven's Door