There are a couple of altcoins I'm currently researching -
VeChain - A coin similar to Walton, it's primarily used for supply chain logistics and product verification. It's not fun or exciting like a lot of these other coins, but I believe it has the potential to change the way logistics are conducted. It also has significant investor attention (PwC, ties with Renault, shipping companies) that indicate that big businesses are interested. Limited consumer application but huge business potential.
TRON - Really awful whitepaper (it's Engrish) but fun and interesting premise - it's a coin used in Chinese apps like Peiwo and a potential introduction to cryptocurrency for a humongous market. Lots of investor attention and the creator, Justin Sun, has ties to Alibaba's Jack Ma.
DNT - A recent coin and something that I will probably use once the technology is better established considering my interest in eBay. I haven't fully grasped it yet, but it's essentially a decentralized eBay or Craigslist for cryptocurrency users. I'm really looking forward to seeing where this goes.
All of these coins have long-term potential.
For me, there's no coins for LONG-TERM investment.Why? Simply because nobody knows exactly what would happened in the future. It is part of business to promise everything to give an assurance to people so that more investors got interest. Though some business experts predicting possible results but keep in mind that hindrances are always behind everthing so don't expect to much.