Interesting discussion you have regarding Luthor and Brainiac. My two cents is as follows:
In as much as (at least Pre Crisis) Superman is vastly enhanced,
physically as well as mentally, he would be Lex Luthor's superior just by virtue of being
Superman. And I know that Luthor
may have 12th level intelligence and then again he may not. What we are doing is guessing based on shaky benchmarks as best.
As to "upgrading" Brainiac from 10th to 12th level, remember the basic circuitry was in place. My cousin, who is electronics engineer, tinkers with a TV set and adds an enhancement or two. That does not, IMHO make him more intelligent than the person/people that dreamed up and built the TV receiver in the first place.
The intuition of the living creature gives it an edge over the computer. Also, there was a mention of
carbon-based lifeforms
Who said anything about Kal-El being carbon based? Is that another presumption? :roll:
Inasmuch that Krypton evolved light years away from Earth, the basic element could well have been silicon for instance.
Like I said, my two cents...