I am wondering if the western companies aren't reluctant to use eastern aircrafts because of their bad reputation in the european/american public. I know it's a shame, but still nowadays most people think that russian planes are not as secure as western ones
I also think that support is an important problem, for civil and for military aircrafts as well. Now considering certification : I though Tu-204 & Il-96 were both JAR certified, aren't they ?
Another problem is that the Tupolev 204&214 and Ilyushin 96 all have a three-man crew, so it implies more personnel costs than a two-man Airbus or Boeing crew.
I'm also wondering if trading difficulties in Russia (corruption & bureaucratic problems) don't discourage western airlines to buy airplanes in this country.... just a supposition though since I'm not a specialist in russian business.
Anyway, I hope the russian aerospace industry will find a way to sell their planes to western airlines in the near future, they deserve it !