There is no true answer to this question because each people could have different opinion and choose different coin. But in my opinion any top coins are gonna be the best candidate as many have said but an underrated nft project that is offering really good product such as mobile game could also bring good return of investment if you choose wisely. If you just want a coin that has good future doesnt matter how much roi you can get as long as its not dumping just choose the top 10 coins or even top 5 coins
The question is what does OP mean by best future? Is that question solely referring to return on investment from today's point of view or is he referring to global adoption and resilience against external attacks of all kinds? Bitcoin has a bright future, maybe not so much anymore from an investment point of view. There are probably popping up coins that do a 100x or whatever. But Bitcoin will have its place for sure.