Meh.
Ion wasn't always around.
I'd assume he's talking about the Corps at the time of the original Crisis. Sure, if you use the best incarnations of every character (Ion/Parallax/etc.) you'd have an unfair advantage.
Considering it took basically every other hero in DCU + a gigantic blast from Darkseid + the full rage of PC Supes, my guess is the Corps would be in some trouble.