Bitcoin is on the decline, but ethereum might be a better bet in cryptocurrency, Brian Kelly told CNBC.

Bitcoin, the most popular digital coin and largest by market cap, was priced around $6,400 on Friday — a staggering decline from its December highs of around $19,500.

But cryptocurrency is still a relatively new industry, and while all eyes are on bitcoin, Kelly, founder and CEO of BKCM LLC, an investment firm focused on digital currencies, said there are other digital coins that investors might want to consider.

"Just remember," Kelly said on "Fast Money" Friday. "Myspace existed well before Facebook. Tech disrupts itself. So, just because you have bitcoin today doesn't mean in 10 or 15 years bitcoin is going to be the leader."

In fact, he said the next big thing in crypto might be ethereum, a decentralized blockchain platform.

"Relative value-wise, ethereum has been trading a little bit better than bitcoin," Kelly said. "I would overweight ethereum at this point."

Here's why.