So far in my limited understanding of all this crypto business it would seem
code - open source so i guess any coin can clone but can all devs manipulate and fix as well as the core btc devs? (not sure)
developers - of course top tier but I think their choices are limited more so that some other alts without hardfork
security of network - cost to successful attack very expensive so I guess this gives it a lot of value
adoption - huge in comparison to all others so again gives huge advantage ..breeds trust there so the attracts most new fiat incoming and it stays there.
I think if another currency can knock it from number 1 spot in terms of volume, MC and tech inovation but it will need to be something rather special or just something just as good that is adopted by a huge company. Why they would not just adopt BTC is a question. The only answer could be that BTC's core code is unable to provide what is needed without hardforking which perhaps the devs could not push through or not get agreement on with mining pools.
No currency rivals BTC yet in the most important areas of adoption and perhaps security (not sure there could be wrong) and surely trust so for now btc staying on top in terms of MC and volume for now.
No currency rivals BTC at the moment. But the Bitcoin development is controlled by BS. It might kill the bitcoin.