Well, since the orig. post doesn't specify HS only or not... I'd have to include Bill Russell due to his post-HS development.
I have heard or read somewhere that most HS coaches back in the 50's didn't really want their tall centers leaving the floor to block shots... It was more like "Get a hand up in his face (sticking or waving hands into the face to obstruct shooter's vision wasn't necessarily illegal back then, as I understand it), then turn around and block out if the shot goes over you". Russell was more likely to leap for a block... No matter how good he may have been at that, it wasn't the preferred way back then.
Of course, while I may be an old guy, I'm not THAT old, so I wasn't there and this is speculation on my part.
I've already talked Concord-only, but this is my list for NorCal players that I saw in person, no consideration for what they did or didn't do after HS... The years in question would be 1980-1994, then 2013-present, since I lived in Oregon from 1995-2012. (obviously, this means I missed Lillard in HS)
No order, except for #1 being Jason Kidd.
Kidd
Payton
Aaron Gordon
Calvin Byrd
Can't make a 5th dude out of the guys I remember seeing in person... but JR Rider could have made my list if he hadn't been off the team more often then on it due to discipline/grades/whatever...
And Ernest Lee! Only saw him once, and he was absolutely killing O'Dowd in the state tourney at the Coliseum until he got in foul trouble and spent much of the game on the bench after the first quarter. Every time he came back in, he'd get a foul right away and be back on the bench... At least two of the fouls looked rather bogus from the stands... So I saw him play maybe 11-12 minutes, certainly not enough for me to decide how great he really was... I still remember him during warmups for that game, working his way around the court, well behind the arc, taking passes from coaches, nailing one catch-and-shoot J after another, Curry range, as easy as layups.
Looked like he had built-in shoulder pads, thighs like a fullback, quick, feathery J from very long range. Wish I'd gotten to see him more...
Just for the heck of it, top Oregon HS players that I saw in-person would include Kevin Love, Kyle Singler, Terrance Ross, and Terrance Jones.
Also saw a bunch of great players from out-of-state powers over the years at the Les Schwab tourney... names escape me offhand. Saw Oak Hill win 5 of the 6 Schwab tournaments they came to while I was up there, only loss to that great 2009-2010 Westchester team in the 2009 final.