While I would no longer classify it as the "greatest," the concert that may have hit me the hardest in a "jaw dropping, heart stopping, mind melting" way was Kiss at the Swing Auditorium in San Ber'do circa 1976. It was basically the "Alive" set, with all of the pyrotechnics and cheesy theatricality that we've come to know and love/loathe. Pretty sure it was my first "real" concert, and the show--together with all of recreational activities going on around me--were almost more than this then-squirrelly teenager could handle.
Sabbath not too long thereafter at the Orange Show Fairgrounds was pretty impactful too (standing next to a guy who got the shit absolutely pounded, kicked and stomped out of him by a couple of Hell's Angels definitely added a “special something” to the vibe).
As slightly more mature (or at least older) teenager, Queen at the LA Forum was pretty amazing. Saw them again a couple years later after Jazz came out and was dazzled not only by Freddie and Brian, but also by the apparently nude fat-bottomed girls they had on stage on old timey bicycles.
In college, maybe Weather Report, Frank Zappa or Yes in the round (in a Timothy Leary state of mind, no less), each somewhere in San Diego.
More recently, Brad Paisley at the Verizon in Irvine.
Lots of clinkers too, perhaps none outdone by Aerosmith at the Forum in the late 70’s. Ridiculously loud and sound/mix so bad that the songs were pretty much indiscernible. The “Toxic Twins,” and probably everyone else in the band, were so fucked up that it probably wouldn’t have mattered anyway . . . .