No it will never match up to the Ackroyd/Murray films but on its own terms its very, very funny, creepy in places, great new characters and it's FUN. You will not see a more fun movie this year.
The basic premise is that a sad loner who hates women (sound familiar?) tries to raise ghosts in New York to bring about the apocalypse. Struggling scientist Kristen Wiig gets fired from her prestigious job on the eve of a promotion and finds herself investigating a haunting with her old pal Melissa McCarthy. Tagging along for the ride is genius/nutjob engineer Kate McKinnon and wise- cracking subway worker Leslie Jones. Together they must foil said nerd's plan while trying to train hopeless man-bimbo receptionist Chris Hemsworth (who gets some of the biggest laughs in the movie).
The plot is ABC but the real joy comes from the interaction with the characters; some of the funniest stuff since Paul Feig's last movie Spy (and Bridesmaids). There are numerous - though sadly brief - cameos from the old cast and plenty of cool new gadgets. My only real qualm was the overly CGI climax but even that was entertaining as hell. Highly recommended. When that opening Ghostbusters beat kicks in it makes you feel 10 years old again :)