Elvis: Early concerts only (ie Sun records/Ed Sullivan period). He was still good when he started playing Vegas in 1970, but he went down hill after a couple years.
Beatles: Cavern Club and Hamburg period. Also Shea Stadium in 1965 and their last concert in 1966 Candlestick Park because of the history involved.
MJ: Not really into MJ, but I would go to see him during the "Thriller" period if someone else bought my ticket.