Agree, too many plants / flowering ones, to mention AND like all fashion things, they come and go in and out of fashion/ popularity, but some last a lifetime never going out of fashion BUT again depending on season, depending on what area of the world as some plants /flowers CANT grow in hot areas where others NEED cool conditions or Arid conditions and all can be popular in those specific regions.
My favourite flowers are Star Gazer Lilies, Roses (but cant grow the Roses as the deer eat them) Rhododendrons, Azalea's, Camilias and many more, some cant grow here in Scotland other are prolific but people don't think of them as Popular TODAY.
Maybe more info from you would get more answers from a wider range of Gardeners.
Best wishes. WeeNel.
I agree this is a very broad question. I guess it depends where you are. Roses, orchids are always regular favorites. You can look at local garden clubs. If there's a club formed that means a lot of people like those type of plants. Look at what the florists are selling if you are looking for a bouquet for your wife or sweetheart. In my local shop, there's a "blue" flower craze. I see dyed blue carnations, daisy, roses, orchids. The flowers were also sprinkled with glitters. Go figure!