I've seen a lot of concerts, and yet there are way too many to name that I missed, or wished I had seen. There are a lot I could have seen, and regret not have going to as well.
One I really wish I had went to, was a Stevie Ray Vaughan show in Norfolk, Va back in July of 1980. It was before he was a true household name. He played in a small bar that was once known as the King's Head Inn, near the ODU campus. He played two sets, and one of our local radio stations broadcasted the first set. This show is one of the better known bootlegs, and a must have. The King's Head Inn was a very, very small place, so to have seen him there, would have been incredible.
Edit: In reference to the side topic of Aldo Nova. I wish I could get a copy of the bootleg being spoken of in here. The only show I have of his, is a radio broadcast from Worcester, Massachusetts (WAAF 107.3). It's only five songs, and part of a Blue Oyster Cult bootleg, as he was opening for them at the time. From what I understand, it was the first concert ever held at the The Worcester Centrum.