I'm noticing the pattern for a good villain here. The best villains Magneto, Loki, Vulture, Nebula, Winter Soldier and etc have redeeming factors. Stuff that makes you want to see them again, deep roots and connections to the main characters.
Where as the fodder villains, Ronan, Whiplash, Malekith, Yellow Jacket and so on have generic backgrounds. No deeper motives than basic (i want to be rich/powerful) or serving as a human shield(basically) for the greater end villain.
I believe Marvel could give all these villains the same fleshed out vibe that the so called "Good Villains" have but simply don't because they have no current intention on them returning and have bigger and much more serious plans in motion for future conflicts involving better villains.