Comics in general had the same problems as sports cards did in the mid/late 80s through the 90s. Everything was wildly popular and massively printed and people actually kept their stuff in good condition for the most part so everything is mostly worthless from that time. The one area that does have some value is highly graded books. Like 9.2+ graded books can be worth some money, but honestly I feel like that's a bubble that can burst at any time really, since there could easily be a huge quantity of a lot of these books that just haven't actually been graded yet.
I guess the moral of the story is you can't really look at comics as an investment, unless you're talking Silver/Golden Age stuff or graded stuff and that stuff is quite risky. If you enjoy comics and want it as something to have in common with the kids go for it. But if you think it's going to pay for your grandkid's college then you're doing it wrong.