Should I stand firm to be CEO?

Between me and my 5 other co-founders, we are deciding who will hold the CEO position. It has come down to me and another founder. I was told from one of my other founders that they thought I should not be CEO because I am a very skeptical realist, while on the other hand, they felt the other founder should be the CEO because they are always optimistic.
To me, being an objective realist is better than being what I consider naively optimistic. Should I stand firm against the other optimistic founder for the CEO position, or should I give in to the notion that optimism is better than realism in the CEO context?

None of what you describe matters. The point is: who can lead, convince others (both other co-founders, future employees, partners, etc.). Everyone likes to think they are a natural-born leader. But most people are not.

Did you start a club in school? Did it work out and grow, or were you miserable? Etc. Try to be objective. It's ok not to be the CEO by the way, if you feel secure in how critical you are to the startup, then that's completely acceptable. You could be a great number 2.

Optimism is good since the CEO is the public face of a company. Maybe you should consider COO where reality is paramount.