TAV have all recieved guidance from Master Eraqus. While its unknown if he is a renowned master, he has taught TAV. Sora on the other hand recieved no such training and the learning curve for him was steep. [SPOILER="Pre Emptive Response AND spoiler argument stuff]While you can argue that Sora may have just simply used the keyblade from the Ven side of his heart, Then he would be equally as strong as Ven from the get-go, which he wasnt. He didnt even know what the Keyblade was untill Leon told him. Further, TAV couldn't stop MX. Thats 1 Keyblade Master, 1 Dark Wielder, and 1 mix of everything against MX and Vanitas. They still lost. and they had armour.[/SPOILER] Sora has defeated Xehanorts Heartless, almost an entire Organization 13, has even beaten himself, managed to beat Sephiroth, Weilded 3 keyblades at once, and has even beat Xemnas who had the power of Kingdom Hearts on his side.
I'd say that Sora's true potential is yet to be seen. He can also drive Gummi Ships. and, even more pointless comparison, Sora could stand up and fight with a keyblade on a Keyblade Glider too, the fundamentals of that weird floaty-thingy that Riku pilots easily resembles a Keyblade Glider right?
TAV are showcases of how the Keyblade can be utilized I suppose. When you think about it, with Terra showing Power, Aqua showing Magic, and Ven showing...i guess the power of light and darkness together (lets go with that >.>), then it's like if Sora focused on one of those traits he could probably surpass them in there fields (yes my thers/their/they'res are never right..) yet he's balanced so you know. doubtlessly, KH3 will see some epic sora.