My all time favorites are:

The Incal - Moebious & Jodo

Before the Incal - Janjetov & Jodo

The Meta Barons - Giménez & Jodo

Fragments of the Encyclopedia of Dolphins - Prado

Nikopol Trilogy - Enki Bilal

The Techno Priests - Janjetov & Beltran & Jodo

Jeremiah - Herman

Megalex -Beltran & Jodo

What do you think about those and what are your favorites?