Who is smartest , Mister Fantastic , Iron Man , Dr Doom , Bruce Banner

Why stark/banner and not stark > banner , are they equally smart or something?

Because I didn't want to pick one over the other.

I've never understood that if Reed is so smart why doesn't he build suits like Tony? Or is Tony only smarter with engineering?

Well he does build stuff, just not suits. He's also not a crimefighter like tony is, so he has no need to build a suit. He's a family member, an explorer, and a scientist. Reed protecting the world is like, his 4th job. For Tony it's his main concern. When there is a threat, like Galactus, Reed invents something to stop him. Galactus has even said that the main reason he can't eat earth is because of Richards. Reed also isn't weapons driven, so why would he build a suit of weapons? Tony would also like to say he isn't weapons driven, but that's quite difficult to say when one wears missiles on their shoulders. Plus Reed has worked in armor before when he needed too, and seemed to be better at it than Tony (Rhodey was Iron Man at the time, and Reed had advanced alien tech at his disposal, but still)

Reed doesn't have to be smarter in every way, and it's actually been explained before that the only reason Tony even appears close to him is because Tony is a better multitasker, and Richards only likes to work on one problem at a time.