Why do some kids go from beginner to 2300 so fast while other kids find it difficult to get better than 1000?
Some people are just better than other people in certain skills. If Karjakin worked very hard, then you probably have it opposite. Carlsen would be the one with unrealized potential and Karjakin the one who has pushed his limits.
Why is Carlsen the best? No one knows for sure, not even Carlsen. Different people are different.
Aronian is inconsistent in the sense he falters at times, especially in the Candidates events. But you don't get over 2800 by losing many games, either. He may suffer from lack of motivation: he is good enough to understand he will never catch Carlsen and be the best over any period of time, this discourages him from putting out the full effort when it might succeed in any given cycle.
Rubinstein and Keres were also among those who rank as all-time greats but never played a title match.
Hey, I'm pretty sure he won't fall below world number 2 any time soon...so probably he'll be around in the next field of candidates as well.
If I were world number 2 and playing in candidates again, I wouldn't find it hard to motivate myself.
I guess you're right in painting him in a Roddick-like light. He comes close but falters in the biggest moments. Also, he needs to add variety to his white games...Carlsen is equally strong on 1. e4, 1. d4 and 1.c4 whereas Aronian seems to rely on 1.d4 a little too much
At age 12, the youngster became a grandmaster and great great things were expected of Karjakin.
The Russians took him in and he was expected to be their answer to Magnus Carlsen. Years have passed and here we are...while a rating in the 2700s is obviously a great thing, do you think Karjakin has not realised his potential in a way that Carlsen has? And why does Karjakin seem to have a mental block while playing Carlsen?
Other Question - Why do you think the world number 2, GM-Levon Aronian, is so inconsistent?