Its pretty much the translation of beautiful or fuckinggreat in gopnik terms ( see life of boris videos for more insight on gopniks)
Blyatiful can also be used for complimenting a gopnitza
Oi kurwa this beer is blyatiful!
Blyatiful in this example is translated to fuckinggreat
Jake: that girl is beutifull
John: did you just misspell beautiful?
Jake: sorry autocorrect haha
John: we are speaking
Jake: *wipes forehead*
John: please never wipe my forehead again