Delores was the very first host. Arnold spent a lot of time with her, testing her "fidelity" and other attentions he didn't give to any other host. She also remembers everything. They've spent a decent amount of time over the first 2 seasons telling us that Delores is simply different from the others. Now we're seeing just how different she is.
I would agree with you. Dolores and Maeve are the two “above” the rest as far as abilities go. Bernard would probably be number 3. They have all been given special abilities to “lead” or do other tasks. Could all hosts be like them? Sure, if you spiked their abilities and gave them the same experiences/knowledge. For this story however the 3 stand “above”, if everyone was just turned to 11 it wouldn’t be much of a battle.