Some of the bounty hunters using eth for transfering of their token.

Some of them, well all bounty hunters and all erc20 token holders need ethereum to send transaction.

And ethereum blockchain is much faster and low fees rather than bitcoin

Not always, ethereum network can be overloaded.

some of the ico project circulate in ethereum so the popularity of the ethereum increase because of the bounty campaigns

Token holders need ethereum, it has nothing to do with popularity.

Am beginning to prefer etherum to bitcoin myself

You gave no valid reason why ethereum is better than bitcoin.