I agree with you - bitcoin is a solid investment and even now still has massive potential especially so given the limited supply of coins.
Although they are marketed in a similar manner (i.e called coins etc) - I do see a difference between the different cryptos. Bitcoin seems like it has a real chance to become an every day currency - there are bitcoin cash machines popping up as we speak. On the overhand ethereum and the others, IMO, are growing because of their platforms and features. Does this sound logical? Either way, interesting stuff to be investing in.