i will first say i never heard lang lang or yundi li with my own ears, so i do not have a personal opinion on their performances. what i want to say is something of a more general nature (and bears no reference to these pianists - whom i still wish i could get some way to hear)
1st. lang lang is 22, yundi li is 19, mei ting is 23 (or something like this, i'm sure i'm aproximately right). can you name me a pianist over 40 years old becoming well known - good pianist, i mean? or without winning this or that competition? probably not.
i'm not saying that competitions are wrong, or that people winning competitions are worthless (i know argerich won several, and same goes for many others whom i profoundly respect). but why can't you make it unless you're a child prodigy and win chopin competition at 18 and leeds at 22? gieseking started touring when he was 25 and never took part in any piano competition; rubinstein, richter, cortot and so many others whom we now name "the great pianists of the 20th century" never entered competitions. so, why do we need competitions now?
2nd. what's the rush with the repertory these days? i read over the web the "repertory" page of some of the young prodigies that emerged during the past few years. come on! kreisleriana at 21, brahms 2nd at 19, and so on - the sky's the limit! and truth is, based on what i've heard/read, that the mentality has changed during the past 1-2 decades: now, the mentality is "if you're technically good enough to pull this through, then go ahead and play it!". look on this forum: tips needed for scales, finger agility, "i need to play faster", "i need to play louder", "why do my hands hurt" (this one usually comes from those who didn't read the posts under "playing faster and louder"). nobody asks "how should i see this passage", "why is this work considered complex", "how should i teach my hands to differentiate the colors",etc. WHY?
i happen to know a pianist - i've heard him live a few times during the past 2-3 years. he is absolutely awsome, better that tones of records i've ever heard. but (he tells me) he wasn't much of a deal in his 20s, so he never won a big competition. Now his in his mid-40s, he is indeed great and he is know here. why isn't a pianist like him known all over the world, but others (that shall remain unnamed here) are?