A Chinese insider here.
Most China Internet companies are more successful not because their foreign competitors are blocked, but they are more agile to move and adapt products/services to local market.
There are lots of examples. Alibaba beat eBay(never blocked) badly. JD is much popular than Amazon.com China which is continuously operating in China for long time. Tencent becomes an Internet empire via QQ, an instant messaging service which AOL, Yahoo, Microsoft all can not find reasonable monetization ways.
Maybe the best counter-example is Baidu with Google nearly blocked fully. But before that, after several years operating, Google' market share is below 30%.