the Moors are weak and unless your game is bugged they often fail to achieve much.
their tech speed is usually rather slow (if you don't believe me, just try playing them) and so far Spain conquered Cordoba in every game I've played so far (except those where I played the Moors or Arabia).
What one really has to be afraid of though are the huge empires.
In the above game Persia had Gunpowder, Patronage and maybe even Cuirassiers when the Seljuks spawned, which let Persia just shrug them off. Also Rome was pretty strong which led to France having Astronomy sometime before 1200 AD. Fortunately I got a great spy to steal some techs from China (Gunpowder, Military Science, Chemistry in 3-4 turns) to be able to keep up. With their strength I suppose that China will even survive the Mongols...Initially I wanted to go for a domination victory, but now I think I can be happy if I make it a UHV -.-