The best you are really going to be able to hope for is buying one that will retain its value over the years unless you get something that is a limited edition or collector model. Frankly the Colts 1911's worth more in 30+ years will be the colts that have gone up in value over the last 30 years and they are going to be out of your price range.
Go with a Colt 1911, shoot it, take care of it, and it will provide you and future owners more than a century of dependable use. Don't get something you are less than willing to shoot, Colt 1911s are built to be shot. I think that taking it out and shooting it will ensure that the gun is cleaned, oiled, and loved the way it was meant to be loved.
Consider it to be an investment in a cherished family heirloom that you can pass on to your children that they can one day give to their children. That sort of thing will make even an ordinary 1911 worth more than what its monetary value.