Hmm have you ever actually been there?
Ciudad del Este is corrupt as hell and there's nothing to see there. Just cheap goods. Pass through it if you're going to Iguazu
Asuncion is beautiful! You don't know what it's like until you go there. I stayed around a week, it was an eye-opening experience. Of course, it's not your London or New York, you have to go out of your way to find the sights. Lots of beautiful colonial churches and palaces to see. International cuisines, especially really good Italian food. I think 2 weeks is a very
long time for just Asuncion itself, unless you just plan on relaxing with maté and spending a lot of time on the river. There are a few national parks with waterfalls and endemic butterflies outside the city and some lakes too, but I didn't go there. I think 2 or 3 days would be enough.
Everyone will probably tell you Paraguay is really poor, and it's very true. There are shanty towns visible from the Presidential Palace and it's quite dirty. But i'm guessing you're more open-minded and adventurous than the average tourist. There is still a lot of wealth around in Asuncion. Paraguay had the 3rd fastest growing economy in the world in 2010 (after Qatar and Singapore). It's definitely worth the effort visiting. For me, the people were the warmest and friendliest in all of South America. They will definitely be kind and helpful to you if you ask them for directions or things to see.