I have done a long, deep and intensive research over days and weeks just in case to diversify a small part of my investments into potential interesting projects/coins. Beside ETH (which wont make any really big gains any more) and XMR I only could find IOTA interesting, while still very experimental. Everything else is damn useless bullshit I would never put a cent in. Even BTC is a bad joke from fork to fork it is becoming just an expensive, overvalued and slow altcoin with no special features.
Simply happy to be invested in XMR.
I did the same research and came to exactly the same conclusion. BTC, XMR, ETH and IOTA are the only ones that are interesting and XMR and IOTA are the only two that I currently have skin in.
Although I do have my eye on a future project as well
https://www.metronome.io/ Blockchain agnostic, worlds first 1000 year crypto currency. It's got a good "story". It's a catchy pitch.