Bitcoin and Ethereum are always suitable for long-term investment. Because many people can not be patient until they make a profit, they usually invest in altcoins and ICOs in the short run so that they can make the most profit possible, but investing in such an ICO comes with risks. Therefore, it is only safe to invest in BTC and ETH.
You're right. Other may choose between these two coins, but the best thing to do is to choose both instead. These both coins are well-established, well-organized and well-managed coin, therefore we can rely on these two because aside from having a good value it also gives a good profits and a long term investments. In order them to continue reigning and giving hopes to us, we must also give back what they've given unto us by simply helping and supporting them to there plans and projects.