I've been looking through a lot of live aid videos on youtube which has left me thinking who were the best and worst acts. For me the best were :
Queen
Simple Minds
The Cars
David Bowie
U2
Paul Young
Dire Straits
George Thorogood & The Destroyers
The Power Station
Spandau Ballet

The worst:
Adam Ant
The Thompson Twins
Patti LaBelle
Joan Baez
Ultravox

Well that's in my opinion anyhow