Ironically, the real star of All-American was Scribby, but I guess his portrait wouldn't have fit the theme of the others.
Yes, Ultra-Man is the obvious weak link in that line-up. Though he is the headliner of All-American, so I wonder how popular he was at the time. (Not very, it seems; he's gone by the end of 1940.)It's a shame they're doing one character per comic, or they could have included Hawk-Man.