Crystal Oscillator not giving correct frequency
First, you have a crystal not an oscillator. 

Majenko's comments on the load capacitor are correct, you should have roughly 30pF on each side, but that's not your biggest problem (load capacitor problems can only pull the crystal frequency slightly). 

The crystal is a 3rd overtone type so it will oscillate at 1/3 the marked frequency unless you add some tuned circuit to encourage it to oscillate at 48MHz. As you can see from the datasheet the fundamental crystals in this series only go to 30MHz.  



You really shouldn't be using such a high frequency crystal anyway if there is any other way- using a PLL internal to the micro to step up a lower frequency crystal is a common ploy. Crystals are best between about 4MHz and 20MHz, higher or lower and there are drawbacks. 

If you really insist on 48MHz for some reason, maybe you should actually buy an oscillator which will have the required crystal, tuned circuit, and amplifier circuitry inside one package, guaranteed to work.