I don't think you are using "popularity" in the right way here. Races are chosen because they have the biggest number values. Orc and Undead have always been the most commonly used attacker races simply because they have the highest offensive values. Faery likewise for its defensive value. What I'm saying is, make ALL races popular choices, for their own individual merits and how they fit into a particular kingdom's setup plans.
"Popular" has to do with being liked. You're confusing popular with necessary. Large offensive values are not popular as much as they are necessary in this game, so Orcs are not as much popular as they are necessary for instance. To compete, you need what is necessary. I'm saying, level the playing field of choices and bring some "popularity" into the race landscape.
Let's talk from an attacker perspective for instance...
You like a setup that does a lot of damage to the enemy? You have Orcs!
You like a setup that has a lot of speed and growth potential? You have Avians!
You like a setup that has a lot of sustainability? You have Undead!
You like a setup that has strong economic advantages? You have Humans!
But their numbers? Those are not that far apart. Right now, the four major attacker races have base offensive values of 11, 11, 12 and 9.5(averaged Undead). It's the extra stuff that makes kingdoms select races for their attackers. Right now, for instance, Human has the most "extra stuff" compared to other races, so it makes them the most "necessary" choice. Their offense is not much different than an Orc or an Avian, but they have superior elite defense plus superior economy and science, which beats extra damage and gains or extra speed and birth rate any day.
For attacker races right now, Humans are well rounded; the rest are one-dimensional. I say we make them all well-rounded in their own ways. Let kingdoms choose based on how they want to play their age; not just on which numbers are the best.