Which are more reactive lanthanides or aluminium?
Since the lanthanides are neither in the same period nor in the same group as aluminium, comparision is actually not feasible. Factors like atomic size and effective nuclear charge tend to predominate such comparisions, rather than ionization enthalpy or reduction potential.

Bear in mind that due to presence of electrons in f-orbital for lanthanides provide poor shielding of electrons farther away from the nucleus. This poor shielding is due to the fact that f-orbitals are quite diffused in nature. Yet, we cannot say anything about reactivity of lanthanides when compared to aluminium.
If you are still a high-school student, I suggest you do not ask such hypothetical questions.