Your placement is fine.
Your routing of the crystal signal traces is fine.
Your grounding is bad. Fortunately, doing it better actually makes your PCB design easier. There will be significant high frequency content in the microcontroller return currents and the currents thru the crystal caps. These should be contained locally and NOT allowed to flow accross the main ground plane. If you don't avoid that, you don't have a ground plane anymore but a center-fed patch antenna.
Tie all the ground immediately associated with the micro together on the top layer. This includes the micro's ground pins and the ground side of the crystal caps. Then connect this net to the main ground plane in only one place. This way the high frequency loop currents caused by the micro and the crystal stay on the local net. The only current flowing thru the connection to the main ground plane are the return currents seen by the rest of the circuit.
For extra credit, so something similar with the micro's power net, place the two single feed points near each other, then put a 10 µF or so ceramic cap right between the two immediately on the micro side of the feed points. The cap becomes a second level shunt for high frequency power to ground currents produced by the micro circuit, and the closeness of the feed points reduces the patch antenna drive level of whatever escapes your other defenses.
For more details, see https://electronics.stackexchange.com/a/15143/4512.
Added in response to your new layout:
This is definitely better in that the high frequency loop currents are kept of the main ground plane. That should reduce overall radiation from the board. Since all antennas work symmetrically as receivers and transmitters, that also reduces your susceptibility to external signals.
I don't see the need to make the ground trace from the crystal caps back to the micro so fat. There is little harm in it, but it is not necessary. The currents are quite small, so even just a 8 mil trace will be fine.
I really don't see the point to the deliberate antenna coming down from the crystal caps and wrapping around the crystal. Your signals are well below where that will start to resonate, but adding gratuitous antennas when no RF transmission or reception is intended is not a good idea. You apparently are trying to put a "guard ring" around the crystal, but gave no justification why. Unless you have very high nearby dV/dt and poorly made crystals, there is no reason they need to have guard rings.
You don't necessarily need a local ground plane for the micro. The local ground can be a star with the central point under the micro, which is where this star is connected back to the main ground, for example.
If you have at least 4 layers, then it can make sense to dedicate one of the layers in the immediate vicinity of the micro to a local ground. If this makes routing too hard or this is a two layer board, just use the star configuration. The main point is to keep the high frequency power current drawn by the micro off the main ground plane. If you don't do that, you have a center-fed patch antenna instead of a ground plane.
The loop from micro power pin, to bypass cap, to micro ground pin should not cross the main ground plane. This is where the high frequency power currents will run. Connect the ground pin to the main ground in one place, but do not connect the ground side of the bypass cap to the main ground separately. The ground side of the bypass cap should have its own connection back to the micro's ground pin.
Digital signals going between the micro and other parts of the board will still have small loop area because the micro will be connected to the main ground close to its ground pin.
Best Answer
You seem to be labouring under the misapprehension that the EFM32 has a built in crystal. It doesn't.
It has, as many microcontrollers do, an internal RC oscillator, which is wildly inaccurate.
It also has "A high speed crystal oscillator circuit", (as well as a low speed one) which is the circuitry required to use an external crystal. To use it you must connect a crystal to it to regulate the oscillations. That crystal must be between 4MHz and 32MHz (higher on some versions of the chip), or 32.768kHz for the low speed oscillator.