Motion would be easiest. Unfortunately, it is very difficult to design a template for this kind of effect that will rely on the size and onscreen width of the text used.
FCPX doesn't really come with all you need to build it in the app itself. You can, however, download this zip file:
http://sight-creations.com/free_special/MotionBasicsbySC.zip
which contains 20 basic Motion generators that were left out of FCPX. In the collection there is a generator called Stripes. Install that, it should be all you need for this.
[Need help installing? http://fcpxtemplates.com/install4fcpx/latest.htm]
Add the Stripes generator. In the inspector, set the Rotation to 90°. Dial down the Color 1 parameter and set the Opacity to 0. Adjust the Size to taste (around 10) and the Width (which becomes the height when rotated 90) to about 34 or so -- just enough to show two lines. You will animate the Height parameter for effect.
Add an Effects > Masks > Shape Mask to the generator and in the Video tab of the inspector, set the Invert option. Adjust the size of the mask to the width of the text you will be using.
Add your text (a Basic Title should do.) Keep everything centered. Use the Text Inspector > Basic > Advanced > Baseline parameter Video > Transform > Position > Y [Baseline doesn't keyframe -- sorry!] to animate the vertical offsets of the text (assumes a single line - otherwise make sure all text is selected before keyframing!) You can use the Video Animation tool to set the Fades with the Opacity control.
Animate the Stripes generator Height parameter to correspond to the fade animations.
Once you have all the basic animation in place, I recommend selecting the generator and text together and creating a compound clip, then using the transform parameters to position the effect on the screen so you don't have to realign the generator, mask and text again in separate moves.
HTH