Bitcoin is still the leading Cryptocurrency as I do not see it's replacement for now. The most important Cryptocurrency for now is bitcoin and it will remain so for unforeseeable future. Many altcoin like ethereum are promising but bitcoin will lead Cryptocurrency!
Bitcoin price is falling while its dominance is growing. It is also the sign of the fact that no one altcoin can replace BTC. Naturally, I am speaking about 2-3 years period. Probably, late some super crypto will appear.