That's an excellent question. I have also taken the decision to stop buying ERC-20 tokens (except for BNB - which won't remain an ERC-20 token forever anyway).

As a major NEO fan, I support NEP-5 tokens, but I feel that I must first say this: I think that NEO itself is insanely undervalued and underpriced right now. If you want something to hold something from the NEO stable then I recommend buying NEO itself! Remember that any (and every) NEP-5 token that does well will pass some of that success on to NEO holders (through the use of GAS). Also NEO generates GAS and also does airdrops i.e. you get other NEP-5 tokens for free! Just by holding NEO I already have free GAS, PHT, ONT, NNC, MCT and recently CGAS too! So just remember that before going off into NEP-5s!

I think the most promising long-term NEP-5s are the DEXs. Switcheo and Aphelion are both positioned to do well, though the real prize will be NEX once it is up and running, probably early next year. I also love THEKEY and consider it to have huge room for growth.