翻译:中国保险市场巨大的需求使各大保险公司在亚洲市场的选择机会更大，吸引了国外竞争者蜂拥而至。

The colossus demand in Chinese insurance market not only enhances the opportunities in Asia for the (local) major insurance companies, but also attracts foreign competitors to swarm in.

“大保险公司”也可翻译成market majors of the insurance industry或insurance market majors或major insurance market players。

The great need of Chinese insurance market widen the alternative for major insurance companies in Asian market, and attract foreign compititors to swarm forward.

The great demand of the China insurance market has made various insurance competitors both in domestic and abroad rush into China.