It's not because he is Asian, it's because he started showing his potential in 2008. People started desperately seeking for "new blood" in 2010, when Kei already was something like "old crippled veteran" along with Del Potro, and I suppose they didn't even realize, that Del Potro and Nishikori are almost the same age with these "Young Guns" (and for god's sake, Dolgopolov is 24! He cannot be "new generation" at all!)
While you may be right, the match final preview on the skysports stream with two commentators, one being Peter Fleming, spent almost 15-20 minutes talking about the ins and outs of raonic's game and how much he has progressed (not takin anything away, raonic has had an amazing season). They spent only a few minutes on nishikori as more of an afterthought and Peter Fleming really did not know much about nishkori's play style and made a prediction based on nishikori's short stature as grounds for Milos winning the title with his serve and power. basically all he said was that nishikori was shy, short, and that he was at a natural disadvantage to a lot of players on the tour. It really shows the lack of emphasis on players like nishikori in western sports channels. They then progressed to talk about federer and nadal on hard court surfaces with no relation to the final and no more mention of nishikori. I may sound petty but one can't deny the preference these channels show. But I'm glad that nishikori can show that he can stand with the top guys with his own unique set of weapons.