On a technical level 'Close Encounters' remains even today a truly amazing achievement, on a narrative one the Spielberg sci-fi drama is for the most part very solid but suffers from a few problems. The film has a fascinating secondary subplot with a group of scientists going to various places around the globe where ships, planes, etc. lost for ages are suddenly showing up. Trouble is the main plot follows a frustrated and abusive near-redneck who has a close encounter and becomes so eaten up and compelled by it and the visions he's having, that his wife and kids are becoming increasingly fed up and afraid of him (he is disturbingly abusive to his family in this) and end up leaving him.
On top of that is the primary subplot about a young single mother and her inquisitive young son (its never a Spielberg film without one of those) which feels a little underdone. This is one of those films where everyone agrees the last 30 minutes are some of the most spectacular cinema made, but its a long 90 minute pre-journey to get there - one which has its highlights but could use some cuts. I love Dreyfuss in comedy films and his great performance in "Jaws", but I basically can't stand him in this, for me anyway character isn't likeable at all - neither is the no hoper of his wife (Teri Garr) and the way their marriage troubles come to a conclusion is unsatisfying (and the film's only real major problem aside from the way too cheery sentimental aspect of it).
Melinda Dillon is a little better as the single mum and the 'abduction scene' in her household is a great suspense piece, but her storyline is plagued by a young kid being a young kid - you either love them or loathe them. Still aside from some patchy scenes in the first half, as things come together and more towards each other they disappear and elements such as the great John Williams score and the superb FX make one forget about the overly lengthy start. There's a masterpiece in here and indeed when the film focuses on the alien subject matter it works brilliantly, but the family scenes sadly are under developed and unrealistic, thus flawing the final result.