The MCU Fantastic Four
To build off of this, galactus has the ability to alter his size to whatever fits his needs at that time. The Power Cosmic pretty much let him do what he wants.
I'll also add that Galactus is so hard for the mortal mind to comprehend, that what we see as Galactus is just how the human mind makes sense of him. Other races or beings perceive him differently.
His size has varied wildly in the comics. This reddit post has a few links to some images from comics:
Here's a couple:
About four times as tall as a human:
Bigger than buildings!
So his size is appropriate to the comics, in that pretty much any size from "that's a big guy" upwards is appropriate.
To build off of this, galactus has the ability to alter his size to whatever fits his needs at that time. The Power Cosmic pretty much let him do what he wants.
I'll also add that Galactus is so hard for the mortal mind to comprehend, that what we see as Galactus is just how the human mind makes sense of him. Other races or beings perceive him differently.