I agree with much of what GalacticStorm said.
Molecule Man is so over-rated. the guy started off as just
another FF villian, then with Secret Wars I, he was made
more powerful, though not by much (he still was nothing
to Galactus).
But then comes along this uber-bulls*** known as Secret
Wars II, and suddenly this annoying pest ebcomes the most
powerful being in the universe after Beyonder.
Thankfully marvel retconned him, sp that he, and Beyonder,
became nothing but incomplete Cosmic Cubes.
But about Molecule Man and Cosmic Cubes, even if he is
more powerful than a full Comic Cube, that doesn't mean he
is on the level of a Cosmic Being. The fact that as a human,
he is capable of a greater imaginination doesn't translate into
a greater power level.
As GalacticStorm pointed out, the Cosmic Cube's powers are
mostly illusion, illusions which last only a short time, and which
don't extend beyond Earth and maybe a few planets beyond.
That's nothing compared to a Celestial, whose powers are atleast
on a solar system level.
And though Molecule Man's human mind may give him greater
imagination that a Cosmic Cube in using his powers, his mind
is still a human mind, with it's own limiations, limitaions which
the Celestials don't have. Also, as I said above, greater human
imagination doesn't mean greater power levels. Magnet, as a
human, is I'm sure capable of imagining all sorts of things to do
with his powers (like control the Sun's magnetic field), but that
doesn't mean he can.
Besdies Eternity and Deathg, I think a fully powered Galactus
can defeat one or two, but I don't think much beyond that.
Phoenix is tough, since she has shown the powerful levels enough
to destroy a solar system, and I heard she is the embodiment of
all life yet to be born, so maybe she is more powerful than a
Celestial, when not confined to a human body?
And yes GalacticStorm, that Franklin Richards thing does seem
to be bulls***, doesn't it?