You know if this list gets long enough, all the Criterion films are going to be mentioned....

But if you have 4 Kurosawa films, I'm guessing at least one is a samurai film so you might want to try the Samurai Trilogy - not quite as good as Kurosawa's films but they don't suck.

One of my big surprises was Sid and Nancy - I didn't think I would like it but it turned out to be a really GOOD film.

I'd also recommend the film that got me started buying Criterions (although it was a favorite long before) was The Seventh Seal - a classic in every sense of the word.

Really though, the reason why Criterion is still around is that they always have interesting films - may not always like them, but they at least hold your interest, which is more than can be said of a lot of other studios.