as my impression dogecoin is just a copy from litecoin
but it is very popular over a period of time
And much faster: 10x
Nope. The reason Doge is sticking around and gaining acceptance is to aggravate Spoetnik.

That seems to be the main reason it's doing well...
Additionally, Doge is still available for ordinary miner with only one HD Video card.
LTC - not.
BTC - out.
No coin is available for ordinary miner with a single HD video card.