check here http://www.netmarketshare.com/search-engine-market-share.aspx?qprid=6 and here http://www.netmarketshare.com/search-engine-market-share.aspx?qprid=4 I guess the answer would be baidu, but is it really matters? as google has 85% share.
Other than Google, Yahoo and Bing the most used search engines are 1. aol.com 2. blekko.com 3. lycos.com 4. altavista.com
Even if there are 100's of search engines out there most of the internet users only cares about Google 1: Google 2: Yahoo 3: Bing 4: MSN
After these three Aol stands fourth.Then astalavista comes into the screen.there are many other SE looks like google too.Say for example: soso com.