Wow, this is an interesting definition of investment. I've always considered my wife to be a blessing, but you are right -- a good wife is a great investment as well.
I've thought about it like this for the last couple of years: Finding a good partner is the most important decision you can make. After all of the promotions and successful business deals/ventures, if you fail to do so, chances are you'll lose ~50%. Easier said than done though.