Watches are bad investments in general. If you want to make money, invest it in FDs, stocks with stable dividends, or maybe even open up a business. Predicting the investment outcome of a watch is damn difficult, as it is marred by demand and supply, fashion trends etc.
Having said that, if you want to be safe, a Rolex or Patek are the safest. Though, imagine all the people who bought those small dial Pateks back a few decades. They are unable to sell em today. Avoid too big (44mm) or too small (34mm) watches. Typically 37mm to 40mm and you are safe. Cause you may never know where the next trend is heading to