I think I'd pick Bruce Wayne; the man's a detective first, hand-to-hand combatant second, and gadget man third... or at least that's how *I* think of him. It'd be great to see him leaning more on deduction than he already does, and less on "tech".
It'd also be fun to see Doctor Doom lose everything and have to start from scratch; he'd be at the top of the Marvel food chain again in no time, but it'd be a fun story to read.
Frank Castle (The Punisher) already has a hefty pocketbook, but with.. say.. Tony Stark's funds... I bet he could contract someone to make him a weapon that's capable of destroying a Sentinel or two (and no, I don't mean a nuke..
).