The park scene is starting to develop in Chile, but it still isn't much so you should try not to see that as a priority. As stated above, El Colorado has the best park set up which when I was there this past summer was two medium kickers and a number of basic rails. Valle Nevado and La Parva, the two resorts on either side of El Colorado also have decent parks, La Parva had a really creative rail garden that was a lot of fun to lap. However, the natural terrain at these three resorts is very flat and rolling, good for building jumps or finding natural hits but if you are looking to scope lines and ski steeper terrain I would look towards the south of Chile.
I skied at a little resort called Nevados de Chillan which was a totally different scene, far less touristy and gave off the vibe of a local backyard ski hill, except the mountain itself was huge and at the base of a volcano. The south of Chile sees far more snow than the three resorts near Santiago, and the terrain is way better but the park scene is little to none and it was much more out of the way than the closest resorts to the city. If I could do it all again I would go back to Nevados because the snow and terrain is better and you get to experience more of the real Chilean culture as opposed to the tourist trap of Valle Nevado