I have seen nothing of Leslie Jones prior to Ghostbusters. I think she was solid, with some definite good bits, but nothing spectacular. My wife also thinks she’s great on SNL, however.
JEDIT: No offense but I’m gonna trust Chris Rock over anyone on this forum.
http://jezebel.com/leslie-jones-fuck-you-ive-been-funny-1749928963
Jones got her SNL shot after Chris Rock told Lorne Michaels (head of the sketch show) to give her a chance, calling her the “funniest woman I know.”