Hi,
you wont be able to "do" south america in 2 weeks - its a huge continent!
I'd say, pick one country and dont try to squeeze too much in :
If you want amazing scenery and indigenous culture, I'd recommend Bolivia (salt lakes, volcanoes, amazon jungle).
If you'd prefer somewhere more european-ized try Argentina (Buenos Aires, and trip to the pampas, wine regions, polo matches, tango, iguassu falls etc).
If you're into hiking try Chile (hike the andes, and the national parks in patagonia are beautiful, Santiago is also a nice city) or Peru (macchu pichu etc).
Enjoy!