He may have been a frightened little boy on the inside, but on the outside Lu Bu was a hulking engine of destruction. He single-handedly turned the tide in battles much larger than Ma Chao's little scuffle with Cao Cao. He wasn't ever fightened when he had free rein to fight, so I think that analysis of Lu Bu is a bit unfair.
Later on, when all the petty lords are fighting amongst themselves it seems like Ma Chao is a great warrior and general. Compare that situation to where it was everyone with an army vs. Dong Zhuo, and Lu Bu's accomplishments on the battlefield are much greater.
Zhao Yun was a good soldier, like Xiahou Dun. He was good at his job, and no doubt full of virtue, but he wasn't even close to the level of a Ma Chao or Lu Bu.
In my opinion I think Zhou Yun is the BEst out of those 3.
lu bu is a traitor
ma chao is just well known for his battle at tong agaisnt cao cao.
but zhou yun saved liu bei's son in middle of thousands of troops and zhou yun was with shu till he was old
when lu bu died caseu he was betryed by his officers and captured.
ma chao died of sickness.