Well, there is the old joke (sorry if it's already been mentioned) "Who was the best bass player in ELP? Keith's left hand". Greg certainly did some cool stuff in the studio. Listened to Trilogy while making dinner the other night.
I heard a boot of him with the Alembic, and it was so tinny, I wondered if the engineer only took the feed from the bridge pickup?
I always find that Lake's heart wasn't really in bass playing (and you can hear it) - he played bass in ELP because someone had to just like Roger Waters played bass in Pink Floyd because someone had to. He wasn't a Chris Squire who relished playing bass or one of the long line of different Jethro Tull bassists who all enjoyed making themselves heard. In interviews today, he even admits that he has lost all interest in playing bass and much prefers playing guitar.
Given the complexity of ELP's music (and the opportunities it gave to a bassist), Lake's bass playing was merely functional, workmanlike, sometimes even pedestrian/listless, nothing more. Mind you, between Emerson's keyboard excesses and Palmer's hypheractive drumming, there wasn't a whole lot of room so that Lake's less than flashy bass playing fitted a purpose. He also had those lead vocal parts to do.
That is not to say that he didn't have the chops of other Prog bass players, just not the artistic drive or hunger. Even Michael Rutherford - not really a dyed in the wool bassist either - was more creative/playful within Genesis. Lake was chiefly the pretty face, romantic and melodic, easily accessible singer within ELP - who also happened to play bass as the music required from time to time (when Keith's left hand was busy wandering off).
And I always found his bass sound and playing cold and heartless as opposed to Chris Squire's which - trebly and even harsh as it sometimes was - was always utterly vibrant and ebullient.