Well, Niccolo Paganini I often hear people say was the best violinist to ever live. he is the one people say sold his soul to the devil in order to be so good. I think David Oistrakh was one of the best in the modern era (died in 1974, so I don't know if that counts as modern, but there are some recordings of him). For a current violinst, I like Anne Akiko Meyers. I don't know how she technically ranks as a violinist, but I really enjoy her playing. I especially like her album "Smile" (2009) if you're looking for something to listen to.