Tocllaraju would be a good one for sure, but it just depends on what season you're going.

There are tens of thousands of mountains in the Andes, so it would be hard to pick "the best" in any category.

Tronador what one of my favorites, but isn't that high.

If you want something high (20K), Coropuna would be a good one, but do acclimatization climbs first.

Sosneado or Vallecitos (the one near Mendoza) would be great.

If you're going guided, it wouldn't be out of the question to try something harder such as Tocllaraju. Pisco or Yanapaccha would be excellent targets for someone with your experience level.

There are just so many peaks to choose from in the Andes. Just find one that looks good and go for it.

I'd add Ecuador, but I was down there in 1990! The high peaks in the country are all day hikes from huts and require basic crampon/ice axe/rope skills. Chimborazo, Cotopaxi, Antisana, Illinizas (north & south). Acclimatize with a few days in Quito and the customary visit to the Equator and Otavalo. As Always: get in the best aerobic shape you can for the best chance of success.

HOWEVER:

1. Cotopaxi erupted a few years back and it was closed off, I assume by now its re-opened for climbing but not sure of the snow/ice coverage, and the hut at 15,000ft was destroyed in the eruption. Also the major peaks require a local guide to 'escort' you.

2. The political/crime/economic situation has deteriorated in the country (narco gangs & such) and is considered out of control, so not sure if I'd even consider going down there. It was quite a nice place in the past.

I'll throw this in for consideration: Aconcagua.

The 'normal' route and the 'crossover route' are both fairly non-technical (the normal route can be walked up in a low snow year) so don't put it out of the question. It would take a few weeks to do the trip (3 at least), but if you don't have any major issues with 14K peaks or basic ice/snow travel skills (no glaciers on these two routes) and you don't mind lining outdoors for two weeks its definitely worth looking into. Climbing permits are required (and are now expensive $1K I've heard. I guess Argentina is trying to use the fees to solve their debt problem!) and guides are required by all foreign groups, but the terrain isn't tough. Research it as I was there in the 1990s and logistics have probably changed quite a bit.

If you only have two days to spare before climbing Yanapaccha and Tocllarju, just hike to Lago Churup and then some short hikes around Huaraz. 2 days isn't enough to do anything in Cuzco and to be back in Huaraz. It takes two days each way just to get to Huaraz from Cuzco.