I was just thinking about this last night. Both men are billionaire playboys with a respectable public face, but are eccentric, as their money allows them to have whatever they want. Both use their vast wealth to create major laboratories and expensive and elaborate technology. Neither one of them have actually super powers. Both men have dead parents. Both have butlers (of sorts) Batman has Alfred and Iron Man has JARVIS. What do you think? I realize their origin stories are different, but the rest seems close to the same.