Aluminium industry prides itself on the 100% recyclability of its products.
On an average, in about 2 months aluminium can may be recycled and reused as an aluminum can, something that you can not say with plastic bottles, many of which are not recycled or end up as other inferior products.
Better recycling regime can help the case of plastic products, but that seems a bit hard to implement.
The good thing about plastics is that advancement in technology has helped a lot in reducing the weight of the containers / bottles and therefore improvement in their usage / enviorenment impact. Growth of bio degradable plastics will certainly help the cause.