I wouldn't consider my wife to be anywhere remotely close to "dumb" - she's quite smart. I think most people would consider me to be smarter than her, but that's only because intelligence is generally judged in a narrower set of areas. I consider her to be quite smart though. Socially, she's smarter than I am. She's certainly smart enough to be competent as an RN, and competent enough to be her hospital's nurse of distinction for her competence & achievements. And just as importantly, she complements my intelligence in the areas where I could be certified as mentally deficient: picking out matching clothes. If intelligence were based upon picking out clothes alone, I'd be riding the short bus to the workshop every day. I couldn't even tell you my shoe size or clothes size any more. I've proof-read some of her papers that she's written, looking for errors. I get pretty irritated when I find stupid mistakes that she should have caught if she had proof-read the paper. I think now though, she's learned that she needs to proof-read her paper first, because I'm not very tolerant of such mistakes. As a result, I've found her latest papers to be virtually perfect.
So, no, I wouldn't marry someone who was significantly less intelligence than I was. However, I'm also smart enough not to necessarily judge intelligence in more traditional ways.