The Russian accent is fake, He has been using the accent for a very long time as it is what got him famous on youtube for his Call of duty commentaries. He started off on Youtube a bit late when it came to doing call of duty commentaries so he had to do something stupid/crazy to get noticed, luckily for him it worked.
Most people who subscribe to him are aware of the fact his accent is fake as he does not try to hide it and tells people quite often. This is one of his older videos where his did a dual commentary with himself as both FPSrussia and FPSkyle http://www.youtube.com/watch?v=dyBGXQDStk4
When he does live commentaries over skype with other youtube members or public events like the paintball he uses his normal voice.