You should see:
1) Spirit of the Beehive (Spain/available on R2-DVD)
2) Aguirre, Wrath of God or The Enigma of Kaspar Hauser (Germany/both available on R1-DVD, I think)
3) Buñuel films like Viridiana, The Discreet Charm of the Burguoise or his earliest surrealist films (Viridiana does only exist in VHS, The Discreet charm.. in R1 Criterion DVD)
4) Roma or something else made by Fellini (Italy/available on R1-DVD, I think)
I don't think you shoud limit yourself to films made after 1990. There is not very much going on in Europe and Asia (or Latin America, or Africa..) these days. I also recomend you to explore Anmerican independent cinema (if you haven't done that already). You should see Gummo, made in 1997 by 23 year old Harmony Korine, the most fascinating and radical film of all films made after 1990 in my opinion. It was hailed by directors like Herzog and Bertolucci when it was released. John Cassavetes, the father of US independent cinema, is also a man you need to explore. Good luck! 
 