Both of these wooden sets are high quality, heirloom toys which can be expanded by buying more sets. They are well-designed and each have fun accessories. These are fun toys with lots of possible constructions. They are green toys, but not cheap in price.
Haba best for kids 5 to 7 years and up, depending on patience and dexterity
Quadrilla best for kids 7 to 9 and up, again, depending on patience and dexterity Image is of Quadrilla from hapetoys.com
Plastic marble runs are less expensive and snap together, making them more stable. They are probably better for younger kids because they won't cause as much frustration. It does take away some of the artfulness of balance in constructing for the older kids, but there is still a lot to achieve. Some of these sets are huge! These below are also high quality and will last a long time.
Quercetti is a toy company which does make an effort to be eco-friendly. The plastics they use in their marble runs are ABS, POLYPROPYLENE, and K-RESIN. No PVC Phthalates. They have sets for toddlers, and some sets are simpler than others making it easy to add on as their abilities grow. (Of course, none of these sets are for kids young enough to be putting marbles in their mouths.) Real glass marbles.
Block-N-Roll must be included in this list, although they can't claim to be "green". They do use USA- made PVC phthalates-free ABS plastics. Their pieces are compatible with Lego brand and Duplo building bricks and Mega Bloks. It's likely kids already have some of these, so it greatly extends even the smallest marble run set.