Comics (over all) have risen significantly over the last decade because they have an inverse relationship with interest rates. They have not outperformed real estate, definitely not the equity classes (indexes) and arguably not other collectible asset classes (have you looked at what some magic the gathering top tier cards have done over the last 15 years?). For every example that someone claims about comics being an incredible investment, we can all find an example of something in a different industry that's performed better.
Two years ago I was looking at a semi up the street from me, it sold for 188k (to a corp), maybe had 60-80k put into it, then sold six months later for 400k no conditions. Now that same property would go for about 450k. A different example, also real estate, the local recreational market in my area has been totally flat for at least 10 years. Prices on cottages have not moved at all due to a number of demographical reasons, but they offer very good investment opportunities for someone willing to do some work. There was a property for 180k that was generating between 16-20k rental over the 12-14 weeks rental period in the summer - not a passive investment by any means but you can figure out the cap rate on that.
The cost and risk of borrowing has been throw out the window in a zero interest rate environment, so money has nowhere to go but into riskier and riskier asset classes. When that speculative money leaves these asset classes when interest rates start the reversing direction (it will be awhile before that happens) everything will go the opposite direction.