Jean Philippe is absolutely superb. The food is of the highest quality and the flavors are complex, varied, and most importantly delicious.
I've only ever had desserts at Jean Philippe but I would have to say that's what you should be getting when you go there. I've tried some of their chocolates which are very good, and a friend once had their creme brulee which he said was top notch as well and cooked well.
But my favorite thing at Jean Philippe has to be their gelatos/ice creams. They are some of the absolute best ice creams I've ever had as they are just so full of flavor that lingers just long enough in your mouth for you to truly savor the wonder. My friends and I agreed that their cookies and creme was one of the best ice creams we've had in our lives. I'm also a very big fan of their dulce de leche
I should point out that the Jean Philippe at Aria and the one at Bellagio do have slightly different options and some of their flavors presumably rotate.
Can't recommend Jean Philippe highly enough