There are indeed numerous strong parallels between Iron Man and Batman: both have origins based upon either tragedy or redemption (a child vowing to avenge his parents murder by fully devoting his life and wealth to fight the type of crime that claimed them versus a shallow, narcissistic, war-profiteer's tale of redemption after being abducted and maimed by a warlord), both battle very real-world personal demons in addition to supervillians (addiction, post-traumatic stress, spurned mistakes of their past coming back to haunt them), both are billionaire playboys (although Bruce Wayne's playboy persona is an act for the public), both are beyond-ingenious men of science, both use their massive wealth to fund advanced ultra-high-tech crime fighting tools which moreover include numerous special battle suits, both have supportive butlers as one of their main aides (Jarvis is actually a human butler in the comics), both have prominent roles within their world's premier league of superheros, both belong to subset of technology-and/or-training heroes arguably more realistic and plausible in strictly relative terms than superheros who actually have superhuman or supernatural powers, etc. For these reasons, Batman is my favourite member of the Justice League and Iron Man is my favourite member of The Avengers.
Of course, that being said, Iron Man and Batman are hardly the only similar tech-based billionaire superheroes: Green Arrow (in the beginning, he was essentially Batman crossed with Robin Hood, to the point that he had a boy wonder sidekick, drove an Arrow Car, and had an Arrow Cave as his base), the Ray Palmer Atom, and the Ted Kord Blue Beetle being but three additional examples that come immediately to mind.
