Bitcoin is the most valued crypto currency and the currency with the highest Return on Investment (ROI).
No it isn't. In fact it is one of the lowest ROI in the top 100.
Which one is the best cryptocurrency next to bitcoin?
It depends what you mean by "best". Ethereum and Neo have contracts. Nano is fast and fee-less. XLM allows staking. KCS pays dividends. Doge has the memes. etc, etc.