The big guns aren't out for the X1 yet. Titanfall was multi platform and the X1 hasn't seen any great exclusive content since near launch of the X1.
Edit: PVZ Garden Warfare was the biggest release this year outside of Titanfall and ended up going multiplatform, and was already on the 360 as well much like Titanfall.
I think the picture will be different once Sunset Overdrive and Halo Collection are both out. MS did kinda shoot themselves in the foot making Forza Horizon 2 on the 360, yet at the same time they probably didn't want to feel the wrath of 360 only owners complaining about no major first party 360 titles releasing in 2014. I'd imagine the 360 gets a cross gen title in 2015 as well.
TDLR - X1 has no games meme.
It's just that simple.
