i've thought of two real biggies, for me anyway.
both have literally album upon album of primo material, and both are almost entirely ignored (altho golden earring has quite the following in europe.)
i've been knowing about wishbone ash since the beginning of my pre-teen music fetish... but golden earring, apart from the two radio hits radar love and twilight zone, was a band i didn't truly discover til a few years ago.
lemme tell ya what a wunnerful~~and wunnerfully rare~~feeling it is to (a) find a band that kicks ass consistently in all the right classic rocky ways, and then (b) find you've got at least 20 albums worth of undiscovered music from that band that you have yet to explore.
switchin aint no criiiiime...
Ok, my contribution to this thread is Legs Diamond -- although they seemed to me to be a 70's band that never made it out of the Hollywood club scene. The music section of the L.A. Times always had them playing the two biggest clubs in Hollywood (The Whisky and The Roxy) rather than as an opening act at the two biggest venues in SoCal at the time (The L.A. Forum or The Sports Arena). So maybe they really aren't one of the "best forgotten bands of the 70's". Instead, maybe they're just a 70's band that is best forgotten. They never had anyone big time and famous in their lineup, but I still think they still recorded some catchy rock tunes that, if nothing else, got some airtime on the local rock radio station out here.