Altcoins cant surpass bitcoin as long it is use on the market. any use on cryptocurrency like on buying altcoins bitcoin is always the way to buy between altcoins. you must buy bitcoin/etherium before you can buy any alternative coins thats why if your hoping that alcoin will surpass bitcoin maybe its imposible. most of the time there are directly use of bitcoin that altcoins can do so for less hassle your option is to use bitcoin if they have the same use on the market right?
as you mentioned, in this case ethereum is the best candidate because it already has a conversion partner with the widespread use of smart contracts, it seems it needs more time to convince many investors, but some altcoins look ready to be successors, another altcoin with real stability is Tether, this coin is also able to make a sense of comfort for price stability on the market.