From John Mendelsohn's December 1969 review of Zeppelin II:

"Whole Lotta Love," which opens the album, has to be the heaviest thing I've run across (or, more accurately, that's run across me) since "Parchmant Farm" on Vincebus Eruptum. Like I listened to the break (Jimmy wrenching some simply indescribable sounds out of his axe while your stereo goes ape-shit) on some heavy Vietnamese weed and very nearly had my mind blown.

Hey, I know what you're thinking. "That's not very objective." But dig: I also listened to it on mescaline, some old Romilar, novocain, and ground up Fusion, and it was just as mind-boggling as before. I must admit I haven't listened to it straight yet — I don't think a group this heavy is best enjoyed that way.

And from John Mendelsohn's March 1969 of Zeppelin I:

The popular formula in England in this, the aftermath era of such successful British bluesmen as Cream and John Mayall, seems to be: add, to an excellent guitarist who, since leaving the Yardbirds and/or Mayall, has become a minor musical deity, a competent rhythm section and pretty soul-belter who can do a good spade imitation. The latest of the British blues groups so conceived offers little that its twin, the Jeff Beck Group, didn't say as well or better three months ago, and the excesses of the Beck group's Truth album (most notably its self-indulgence and restrictedness), are fully in evidence on Led Zeppelin's debut album.
...
The album opens with lots of guitarrhythm section exchanges (in the fashion of Beck's "Shapes of Things" on "Good Times Bad Times," which might have been ideal for a Yardbirds' B-side. Here, as almost everywhere else on the album, it is Page's guitar that provides most of the excitement. "Babe I'm Gonna Leave You" alternates between prissy Robert Plant's howled vocals fronting an acoustic guitar and driving choruses of the band running down a four-chord progression while John Bonham smashes his cymbals on every beat. The song is very dull in places (especially on the vocal passages), very redundant, and certainly not worth the six-and-a-half minutes the Zeppelin gives it.

Or, the Dec 68 review of The Stones' Beggars Banquet, which doesn't mention the album at all, instead gives a meta-history of the Stones' career.

And, from the earliest review I could find, a Nov '67 review of The Doors' Strange Days:

As was strongly hinted in their first album, the Doors conceive their efforts primarily in terms of drama rather than in terms of music. The music is not meant to be particularly virtuoso or experimental. It is played to be dramatically meaningful. Before they formed as a group, the Doors were, individually, students at the UCLA drama school.

It was a unique qualification. Beginning with long hair and patterns of dress, rock and roll has become increasingly visual. Jimi Hendrix and the Who seem practically primitive next to the Doors. Rock and roll has become theatre.