A few thoughts: An all-time classic genre comedy, Ghostbusters balances humor, science fiction theory, fantastical elements, and some light horror in a way that blends together perfectly. Quite possibly Bill Murray's funniest performance, as well as the best from Harold Ramis and Dan Aykroyd, a trio of unique and hilarious lead characters who play off each other perfectly. Not only has this movie aged well (apart from a few of the special effects are not so special anymore), it is one that still holds a special place in the hearts of people who were raised watching it. Maybe this is just my nostalgic bias or my love of '80s movies, but if I were to name the greatest comedies of all-time, this could very well find a place in my top 10. It's filled with great quotes and funny moments, and even after watching it dozens of times I can still sit down and enjoy it in new ways every time I put it on. I haven't seen the remake (no interest in it), but I can say you'd be better off just sticking with the original. It's a classic and I love it.
Who would I recommend it to? I normally wouldn't say this, but...anyone. I really can't think of a person who shouldn't watch this movie.