Well... in a nutshell:
It helps to play the previous games just to get the gist of Monkey Island and some of the inside jokes that's thrown around in Tales, but you could probably play without playing the previous games. I recommend that you play the other games anyways just because they're fun and it's Monkey Island. Luckily there are the two special editions already out if you want to play the previous games.
I don't care, I said 40 hours. It's gonna be 40 hours. Player Be Damned!
-Ron Gilbert, MI2:SE Commentary