According to Weekend Gardener, while no single fertilizer is proper for all plants, its most highly rated fertilizer is alfalfa meal with an N-P-K ratio of 2.7 - 0.5 - 2.8. Weekend Gardener claims that this type of fertilizer is easy to find, balanced in nutrients, and fast-acting in the garden.
Weekend Gardener also goes into great detail about how the perfect ratios of nitrogen, phosphorus and potassium can make the largest difference in terms of providing a plant's needs. No two species of plants have the same dietary requirements, so there are a wide array of formulations to meet every need. The health of the plant in question is best served by researching its specific care requirements.