99.9% of altcoins have no reason for existing beyond pump and dump speculation. Bitcoin would be your best bet.
Some coins exist for pumping and dumping you are right but I don't think the percentage is 99.9%. This percentage is too exaggerated. I can give you many examples which are very very important for the ecosystems. Some of them have big market cap and some of them have small marketcap. Like Ethereum, Waves, Nem, Gridcoin Research, litecoin etc...
But one of the best bet is BTC thats sure.