Yeah, they've never put out a 'best of'. Who Made Who, the Maximum Overdrive soundtrack they did, is the closest thing to an AC/DC greatest hits, but being made for a movie, it misses out loads of songs (and only has Bon Scott song).
All their albums definitely have songs that aren't as good as the 'hits' and more well-known songs. BIB and HTH are obviously the 'big' albums, but I also think Dirty Deeds Done Dirt Cheap is one of their best albums, along with Ballbreaker, which I think is quite underrated. Their last album was very good too, I thought.