It would be easy to imagine that all superconductors were metals, and that a large number of different metals would superconduct given a sufficiently low temperature. However, this is not the case.

Two common low-temperature superconductors are lead and mercury, although an alloy of tin and niobium works at higher temperatures than these. It is interesting to note that these metals (except niobium) are in very close proximity within the periodic table, and are relatively poor conductors at room temperature: indeed, there are good reasons for this.

(Periodic table showing superconductive elements.)
Image taken from Superconductors.org

In order for Cooper pairs to form, the interactions between the lattice structure and the valence electrons within the metallic bond must be of the correct strength. If they are too weak, then it is difficult for the electrons to exert any force on the surrounding metal ions. Conversely, if they are too strong, the electrons cannot move very easily within the metal. The reason why metals close together in the periodic table will sometimes form a group of superconductors is that the key to determining the strength of the interactions is the ratio of valence electrons donated to the delocalised cloud against the atomic mass of the element. Needless to say, this correct ratio will repeat periodically as the number of valence electrons and the atomic mass increment through the table.

This is also the reason why good conductors at room temperature which are close to these in the periodic table--for example; copper, silver, platinum, and gold--do not become superconductors at low temperatures: the interactions between the lattice and the valence electrons are simply too weak.