Well, many people regret for not buying BTC in 2010. However, it is understandable that BTC was new and people tends to have doubts. It is the same for other cryptocurrencies.
It is still not late to own BTC and other cryptocurrencies.
Yeah but nobody will see back those numbers
For example it is indeed true that:
100$ invested in 2010 would give you back 75 millions now, but
100$ invested in 2013 (december) and you will "only" have 350$ now.
The rate of return is going down and a lot of us won't see, not million but x1000 returns.
And remember, no one lives forever to wait for those returns.