I fly the CRJ a lot; in real world (in the US) CRJs are also very common. So when I looked at Davor's list, I was thinking: why are they all Boeings?
So I did an experiment for you: I got the list of every pilot online on VATSIM a few times, put it together, identified the aircraft types, counted them, and averaged them over the multiple times I repeated the experiment. Here are the most commonly filed aircraft types on VATSIM:
B738 101
A320 41
B773 37
B772 34
B737 26
B744 20
A319 18
B763 16
A321 12
B752 10
Out of hundreds of flights, only 2 were CRJs on average! I am the minority.
Point is, if you want to create a VA, it would be smart to include aircraft types on your roster that are mostly used on VATSIM anyways. And those will be variants of B737, variants of A320 family (319, 320, 321), variants of B777, variants B767, and of B747. If you want a sixth one, add variants of B757 to the list! I am sure controllers would love to see B757s (because they demand special wake turbulence separation).