Not sure what Leo has in common with the others in acting ability, other than you apparently don’t like any of them.
I don't know what his reason would be for the comparisons he mentioned, but mine would be the fact that they would all be miscast in those rolls, just like DiCaprio is miscast here.
DiCaprio may be a capable actor, but he's not believable in the role of Hoover. He just doesn't have the gravitas or stature as a person, not to mention age.
For this movie to work, you'd have to have someone like a Frank Langella, Christopher Plummer or Max Von Sydow, but a generation younger. I'm not exactly sure who that would be, but I know it's not DiCaprio.
Gangs of New York for example. Daniel Day Lewis can put some fear into you in a role. DiCaprio is like a chick with a little knife.
Outside of Hollywood, there's nobody who wouldn't smack him upside the head if he ever so much as spoke loudly to them.