I think Altcoins have a better probability to nets bigger profits in the long run, if you just choose the right projects. Bitcoin and Ethereum will not, imho, have the x10 or x50 chances any time soon. But smaller projects which are promising have a lot more room to grow as exponentially, you just have to do some research and find the gems.
I agree to you, there are lots of potential coins that really have high chance of earning huge profit compared to bitcoin and ethereum. But the problem is how to find that gems now.