Well even if China won, they would still be pretty messed up. What this does do though is it probably keeps the Golden Age of Islam going longer rather than just abuptly ending. Heck we might still have an Islam based on unity and learning rather than shiite/sunni splits and fundamentalism, that sure isn't bad.
Two points: alltough classic Islamic civilisation was brought to a definite end by the Mongol invasion, one should keep in mind that Islamic civilisation had already been in a slow but steady decline since the 11th century.
That decline was the result of the decline and/or collapse of the three great Caliphates, and the fact that they were replaced by smaller, less stable, and relatively short-lived Muslim states.
Political instability weakened the Muslim world, and even without the Mongol invasion, the Muslim world would definitely be past its prime.
And the second point; even if the Chinese (and with this, I assume wolfstar means the Song) manage to repel the Mongol invasions, then that won't change much for the Middle East.
The first actual Mongol conquest of territories in the Middle East took place under Chormagan during the mid-1230's, and Chormagan's campaign was started in 1230. Ögedei's invasion of Song China, the first Mongol campaign againest the Song, was started when Chormagan already had much of Persia and the Caucasus under his control.
And Hulegu's invasion of the Middle East, which was aimed at conquering the Caliphate of Baghdad (Chormagan had avoided any confrontations with the Caliphate because he didn't have the manpower for that), was started long before the Mongols gained the upper hand in their war with the Song.
So in other words; the Mongol conquest of the Middle East would still happen, even if the Song manage to defeat the Mongols.
Eastern Europe and Russia might not be as messed up in the long run and Russia's historic xenophobia might be lessened greatly. What we know as "Western Europe" might actually extend to the Volga!
I agree with this; Russia suffered tremendously from the Mongol invasions, and even though I'm not an expert on (pre-Mongol) Russian history, I do know that Russia was as least as (if not more) developed as Western Europe prior to the coming of the Mongols.