This is tough. Certainly AC/DC in 1978 with Bon Scott was awesome. Stevie Ray Vaughn in 1984 was amazing. I saw Rush every year starting with the "A Farewell to Kings" tour in 1978(?) until 1984, then again in 1997 and every show was awesome. Queensryche on the "Operation Mindcrime" tour in 1989 (I think) was mind-blowing. Van Halen every year until 1984 when they broke up and every show was as good as the last. (I never saw Van Hagar). Ted Nugent 4 times in the late 70's/early 80's - very wild. Honorable mention to Boston in 1978, The Police in 1983, Pat Travers in 1981 and of course Iron Maiden and Dio over the years. For recent concerts the Iced Earth with Evergrey/CoB has to top the list. Unfortunately, I haven't seen SymX yet - they need to come South sometime!