I'm torn on giving it a marginal 3/5 or 2.5/5.
There's a lot to like, but it's ultimately a middle of the road movie. I loved the opening. The 3D, ghost designs and special FX are actually quite good. I think, for the most part, the 4 girls have good chemistry but man oh man, did a good chunk of the jokes fall flat. If you've seen the trailers, you know some of the moments I'm talking about--like the crowd surfing joke in particular. Leslie Jones is basically a loud, walking stereotype. She has a few lines that are funny, but almost everything with her ends with an exclamation point which becomes a bit old and grating. The villain too (a cliche evil nerd), is ultimately weak, and I'm not even 100% sure why the hell he was doing what he was doing, but it paves the way for a weak climax. I really do want to see where they take this franchise though. The new universe and characters are likable enough to deserve a sequel as well as a better script. There was so much potential but it never quite took off. It's at least better than Ghostbusters 2 but nowhere near as great or quotable as the original.
But relax, it's not a total abysmal failure. Harold Ramis is not rolling in his grave right now. Go in with low expectations and you'll likely enjoy it. I'd seriously like to see the sequel fall into the hands of someone like writer/director Shane Black.