To me hardest of these to sell to the GA would be the first one.
Convincing people Galactus is more powerful should be easy if you do him correctly and not make him ... You know... a cloud.
Doom's iconic look absolutely screams ruthless ambition so that should be an easy sell as well.
Telling the GA that anyone is smarter than the MCU version of Tony Stark? Much tougher in my opinion. He's been the undisputed genius/inventor of the MCU so far so I think it will take something pretty significant to dethrone him of that title. Can it be done? Sure, but I think it will take some skillful writing.
Regardless I am EXTREMELY eager to see what they do. Super psyched!

t: