With the way things unfold currently, yes, bitcoin
might be the most viable (and safest) coin to hold long term. More and more people, including governments, financial institutions and other large names in the economic and financial industry is checking out on bitcoin, particularly its blockchain technology. Multiple regulations have also been placed to protect people from being scammed, so that is a plus. Compared to the situation of the Dow, gold, oil and other traditional assets, bitcoin is in a pretty good shape. While that isn't enough basis to go all-in for bitcoin, it still is sufficient facts to get some paper going down the way of the coin for long term.
This is a given. There isn't a single crypto even coming close to overtaking Bitcoin right now. So the answer is a clear yes!
ETH is a really promising coin, tbh, and that is coming from someone (me) who never owned a single coin of that in my entire crypto lifetime. With the way how ETH is utilized, I can see that big investors also have a keen eye on that coin, particularly its dapps which already produced numerous interesting projects.