What does shepard have that makes him as good as the squad members?
Here's a possible list
a) A will stronger than iron. Liara noted that the becaon would have destroyed any other mind.

Determination. This is different from having willpower. This quality tells everyone that what shepard says is going to be done gets done even when it seems hopeless (anime fans may reference the same quality in simon in gurren lagaan)
c) Combat skill. Self explainatory especially since the game penalizes the squadmates damage to make shepard a star
d) Versatility. Form covert ops with Thane to pure arena combat with Grunt, shepard can adapt to the situation as required
e) Intellect. Shepard is not stupid, even if the player chooses the most stupid option possible, the option will never be truly idiotic because they game never lets you.
f) Ability to trust without being naive. Unlike Jacob, shepard trusts people to do their jobs and they won't shoot him in the back if they don't demostrate problems. For example, he doesn't give Tali the "aw you're a weak little quarian, stay on the Neema where you're safe" attitude and he straight out tells Zaeed that he does't want him on the ship after Zaeed shows his rash behavior
g) Ability to listen to experts. He doesn't force EDI to go through the omega 4 relay based on faith of getting through nor tell samara she's stupid when she proposes the biotic bubble. This is very different from intellect as it is more a recognition of what you don't know and that others know more on the matter than you
h) Unique access to information. This includes predominantly, the Cipher, which currently only 3 people (unless spread) have