Old coins can still be profitable, they've been replaced by newer coins because most of the new ones have a higher market cap. Just because other coins have a higher market cap it doesn't mean that they're profitable than the lower ranked coins. Always remember that each coin has it's own kind of price movement not all of them have the same gains and losses so the potential to profit from old coins will be there. Last year ripple had the best improvement even though it's market cap is not high as Bitcoin.
It's depends to a people or coin holders but i believe that old Coin is the most potential Coin that we need to invest .It is all because some of the old Coin are fully develop and many people around as now holding old Coin and wait foe the best time to sell and earn. I believe that old Coin is amazing, we are now holding new coin to make it old and sell when it will fully develop and its price rise up high.