a true kryptonian 'superman' grown and trained in the presence of a yellow sun then sent to earth is basically god.
the superman we know was a farm boy that happened to have superpowers
if you gave batman krypton cells.. well, you have god.
even goku cant compete with that power, sorry but no
goku is damageable by being physically hit, superman is not.
he has 'passive invulnrability' and goku can be *****-slapped when his guard is down
( vajeeta does this in an episode )
and he's not even the most powerful kryptonian and he was never properly trained, only taught by his crystals
( unless your including alternate universes, expanded story-lines.. yadda yadda. )
goku has been to the end of the universe and trained by all the greats his whole life
the average sayan only has a power level of about 3000 without this kind of mental and physical training
i would go as far as to say sayans are unimpressive compared to the 'just awesomeness' of kryptonians
and, everyone has their flaws before you point out kryptonite
i'll just point out that a regular disease put goku down for half a season.
seriously.
what? just no.
so, kryptonian, it's the only real choice here!
let's be honest who wants to be a giant ape when you can be batman+superman in one
( seriously, superman is a dumba@@ he could benefit
from batman's mental capacity quite allot. )