new crypto coins emerging. How hard is it to create a cryptocurrency?

A. Not hard at all. Search "foocoin and barcoin" if you want to get started.

B. In most cases, people make forgettable cryptocurrencies where there are hardly any significant changes other than number of coins produced, timing of production over the long term, and block times which control coin production over the short term and confirmation times (and also bandwidth requirements). These coins with rare exceptions are ignored.

C. It's very common for people to make currencies with a "premine", emphasis on the "mine." That is, they award themselves some number of coins before even starting the process, on the presumption that if their coin goes up in value they will be rich. This is often presented as "development fund" or "foundation" or "charitable contribution" but the effect is the same. If a new coin has more than a couple of testing blocks mined, it's generally considered a scam (read: even worse than being mostly ignored).

D. One actual good idea that's been developed in altcoins is to base mining on "proof-of-stake" rather than "proof-of-work", or to try to make the "proof-of-work" ASIC-resistant (memory-bound, for example, rather than hash-speed bound) This is basically an attempt to prevent mining from being dominated by people who've invested in specialized equipment, as has become more-or-less the case with Bitcoin, and to prevent a long-term risk of a 51% attack.

E. One aspect that hasn't received enough attention is long-term bandwidth requirements. Bitcoin has developed a database of over 10 Gigabytes that needs downloading before you can run a full node, and it's growing fast; this is a barrier to entry that limits the number of people running full nodes. Also, Bitcoin's protocol requires bandwidth and compute power that scales with the product of the number of full nodes and the number of transactions. In the long run this will constrain full nodes to large servers, further concentrating power and further making an attack on Bitcoin by subverting full nodes feasible. A new cryptocurrency with some kind of built-in plan that limited the necessary bandwidth while preserving reliability and the possibility of high-volume use, would be a good thing.

F. Another idea for a cryptocurrency would be a built-in decentralized market in digital goods. The "good version" is frequently considered as a "decentralized stock market" or similar. It could be easily extended to just about anything that exists as information, but that kind of extension is a bit of a touchy subject, because you know, right, what would get traded. You'd basically have millions of minor crimes of copyright infringement, and the commercial exchange of evidence of _major_ crimes such as sexual abuse of children. If you generalize a cryptocurrency to a general digital market, and maintain no way to prevent it from being used almost exclusively for criminal purposes, there will be extraordinarily intense efforts by international law enforcement agencies to take it down -- possibly in a way that results in banning cryptocurrencies in general.