Especially in a medieval society as Westeros. Ned seems like a decent and a nice man, but not particularly charming or someone to be afraid of. However in a medieval society if you are nice people might see it as potentially weak, especially if one of your bannermen is the House of Bolton.
I can understand why people were loyal to Tywin, if you were not, he might go ''Rains of Castemere'' on your ass.
Robert Baratheon is fearless but also charming and gregarious, that is why even his enemies bend their knees. I can understand why people followed him to remove a 300 year old dynasty
Stannis might be hard, but he is just man. He is always fair, so I can't understand why inspires loyalty, that they are willing to fight for him in a snowstorm.
Even Balon Greyjoy makes sense, someone who is fighting for the old way. He is uncompromising when it comes to the way of life of their ancestors, ironmen. That is why people were willing to fight a Rebellion for him. Unlike Ned, who married a southerner and even adapted some cultural southern character traits (probably because of being fostered by Jon Arryn and marrying a Southerner). He is probably the most ''Southern'' northern Paramount Lord.
But he was still able to inspire loyalty, why?
Is Ned just an anomaly?