It's a great analogy. I played Runescape as well and it was interesting to see how people behaved around these rare items. I think the only rare item I had was a rubber chicken but it was untradable. :D

The rare goods don't have a lot of uses - just a store of value and a status symbol. Actually cryptocurrencies have much more - medium of exchange, smart contracts, doing stuff in a decentralized way etc...

I see a lot of similarities - there is a limited amount and from time to time, someone loses it or destroys it... In the meanwhile, money is constantly generated from somewhere - in real world by the central bank, in the game from NPCs etc. You have to work, trade (or alch longbows) for money. Then you can either buy something useful for it (an armor in game, a car in real life) or you decide to spend it later and exchange it for something better to keep the value. Because there are new and new players entering the game, commodity items (such as armor) become cheaper and cheaper.

But there are also some differences between Runescape and real life - rare items cannot be divided, there are no taxes and there's only one single currency in Runescape. Gold behaves differently compared to real life. If something really bad (a hack) happened in Runescape, the game operator can decide to reverse it and restore from backup without the risk of something like an ETH/ETC split.

However, the biggest and most important difference is that in Runescape there were just a few days when Jagex (aka the government) centrally decided to release some items. In the real world, everyone can create their own "rare item", a new cryptocurrency. And it requires a lot of studying to predict which crypto makes the most sense in the long run.

Sure, you can filter out the shitcoins and the ICO ponzis... But how to decide whether to trust in Bitcoin, or Litecoin, or Ethereum, or something else. I honestly have no idea. I don't feel like buying a little bit of all the top 20 coins... even though it may be one way to do it. For example recently I made some money with Ripple but I don't like Ripple because to me it's a weird combination of currency and a "rare item". Ethereum is too reliant on one person, Bitcoin has been in an internal conflict for a long time, Litecoin seems more like a temporary solution rather than solving something new...