What paint would paint alumimum and wood siding equally well?

If it is bare aluminum and wood siding, they need to be primed prior to painting. The best primer for aluminum is a water based primer like zinsser's bulls-eye 123. The best primer for the wood siding is an oil-based primer such as zinnser's cover-stain. You want to use a water-based top-coat on both surfaces to give it better color retention, and durability through harsh weather conditions. If it is already painted, sand down parts that are coming off, pressure wash the surface, wait 24hours to dry and paint again. Remember, the paint you topcoat it with is only as good as the coating underneath it.