Chatellerault likes mythology. That's the only reason she hopped onto the vessel known as Type-Moon, who not only borrows everything you can think of from mythology, but built their own massive mythology. Whoa...
Of the Type-Moon stuff, she's thinks Fate/Zero is awesome (Emiya Kiritsugu and the dungeon bypass! Irisviel von Einzbern's driving! The King of Conquerors and Waver Velvet as the most awesome bros ever!) and Fate/Extra has pretty cool Servants because... well, it has Robin Hood.
The rest of the stuff? Well, she just wants to see how they intersect. That's all.