Don't know how you rank the best new species of plant for a year, any year, but for 2014 it's a Dracaena from Thailand, a damned big, rare Dracaena. There are only about 2500 of them alive. How does science miss something as big (40 feet or 12 m tall) as this for so long? First, it's not particularly easily accessible, which is often the case for new species finds, but in this case not small and insignificant. Second, the genus is not hard to recognize, and people who saw it probably did not realize it was so distinctive, something only an expert in the group would know. At the link above you'll find the rest of the top ten new species for 2014, but this is the only plant. Molecular data has broken up the old massive lily family, so now this genus belongs in the Asparagus family, Asparagaceae.