How many people got burnt in the dotcom crash? In the financial crisis of 2007-2008? Black Monday of 1987? Did all of those people swear off investing in traditional equity instruments forever?
Let's also make sure we understand that the S&P500 (or any stock ownership) is owning _business(es)_. Businesses make money, and they return that money to their owners. Bitcoin is purely speculative and depends on someone else buying it from you, presumably for more than you bought it for. Good luck finding another batch of suckers to fall for this after that last round.
Crypto is... None of these. Whatever crypto is or will become, gold it, currently, is not.
As far as 5 years from now -- who knows where it will be trading. I suspect it will be higher than it is now, but there's never a guarantee on any of this.
My father-in-law didn't know what Bitcoin was in 2011, nor were the sort of newspapers he read covering Bitcoin in prominent articles. Neither of those things are true in 2018.
Obscure for who? I doubt very much your average grocery store cashier, barber, or airline pilot had ever heard of Bitcoin. The farthest-back data I can find (from 2013) shows BTC had a market cap of ~$800 Million. At its peak, it was over $600 Billion. Amongst the HN crowd, BTC was not obscure in 2011—you're right.
MtGox wasn't a secret. It was relatively well known and covered in the news, and I don't mean tech news. 2011, maybe 2012, was when bitcoin entered the public lexicon and it's only become more and more ubiquitous since.
A comparison that's way more appropriate is tulips, but even so tulips aren't used as tokens in money laundering scams.
As opposed to the US dollar which is constantly used in money laundering scams perpetuated by some of the biggest names in global finance?