C'mon, no votes for GTR yet? Actually the best for me was Emerson, Lake, and Palmer...errrr scratch that, I think it was Cozy Powell behind the drums. Keith Emerson's keyboard solo was something to behold.
Best buzz came from the Deep Purple reunion concert. Some guy just came walking up the aisle with literally a garbage bag full of doobage. It did provide for entertainment after they blew a fuse on the stage when they tried to fire up the pipe organ.
Other than that the best would line up as Rush, Rush, Rush, and Rush. But the worst concert I went to was also Rush, but that was at the Cap Center in D.C., and the design of the place created the worst accoustics imaginable, so it ended up being about the only concert I went to that I can say I did not enjoy.