We could pick any number of gold-like commmodities, but like Bitcoin, gold has had a history of large expenditures to acquire it. Both are buoyed by that past.
So many tokens and blockchains are coming out with incremental improvements or niche capabilities, but in the end I think consolidation of market cap is inevitable. I think it ends up Bitcoin as store of value, Ethereum as contracts/api and a large amount of application specific token/chains. Most applications would be backed by ethereum (like most tokens are now), but ones like Ripple could definitely be top 5.