I'm not sure i agree that Itars, Ambas and Ivits are absolute no-brainers. Maybe it's just me who don't play these 3 specific factions a lot, but I have to put in a lot of thinking when using them (while my Taklon, Terran or Firak games are much more streamlined). But then again, this might be a matter of being more or less used to play a certain factions.
The real strenght of Ambas, Taklons and Itars is that they are very versatile. They adapt well to a very high number of scenarios. This is why they get picked a lot (and often perform well, I'm not denying all these races have powerful abilities).
Other factions (e.g. Geodens, Firaks) are also good, imho, but can be picked in a more restricted number of settings. In the right context, however, they can be as powerful as the others.
I'm just not sure the same can be said about gleens, bescods and lantids. The last two in particular I've seen perform abysmally even in settings where they should have theoretically done well. But as I said, I'm not sure about this, would gladly hear other opinions.