Making things harder, Hawkman, Green Lantern, and Wonder Woman are technically All-American, not National. That could change the game a little bit.
Assuming National-only, obviously the top of the list is anybody who got his own title without a crutch, Superman and Batman. They also kept their anthology spots and got World's Finest gigs.
After that, I'd suggest anybody who was in the JSA--All-Star was a "tryout" book, after all, and if you made it there, then you got your own title (Flash and Green Lantern did exactly that). So in the early days, the members would only be characters with the potential to launch on their own. That would be the Spectre, Dr. Fate, Sandman, and (shockingly, in my eyes) Hourman. Starman's also a possibility for the same reason.
I might also assume that Leading (and thus the Seven Soldiers of Victory) was originally intended for the same purpose, though I don't know that for sure. If it is the case, though, then the Crimson Avenger, Star-Spangled Kid, Green Arrow, Shining Knight, and the Vigilante would also be near the top of the heap. Probably not as high, though, since the team book didn't survive. Which brings you to more than ten, I realize.
And it's probably no coincidence that Jon came to similar conclusions by looking at who ruled the cover spots.
On the All-American side, you have a similar reasoning, except that nobody started with a title. Flash, Green Lantern, and Wonder Woman are the obvious top choices. Following them, you have Hawkman (the mainstay of the JSA and Flash Comics), the Atom, Johnny Thunder, and Dr. Mid-Nite. I don't count Mr. Terrific and Wildcat, since they seem to have been last-minute additions, but you can.
Controversially, I'd probably also add the Red Tornado. Why? Because she's the only Golden Ager I can think of who was referenced and given a kinda-sorta legacy in the Silver Age. To me, that suggests that Gardner Fox didn't think Ma would fit into a JLA/JSA crossover, but thought there was enough brand recognition to reuse the name and mention the original.
Johnny Thunder and the Star-Spangled Kid may both need to get dumped off for getting replaced by their distaff sidekicks (though it puts Black Canary on the All-American list). I'd say the same goes for Green Lantern, replaced by his dog, but he at least keeps his All-Star gig and keeps his name on the title.
Obviously, if you're talking about both National and All-American, that should give you a more solid field to choose from. And no, I don't know how to count Robin, either.