Andrea Bargnani is a joke today, but he's still the most meaningful comparison. It feels like faint praise to say that Kelly Olynyk is a rich man's Andrea Bargnani whereas it's pretty frivolous to say that he's a poor man's Nowitzki, but Andrea Bargnani IS a poor man's Nowitzki, after all (very, very poor).
Olynyk is a lot closer to Bargnani than he is to Dirk, but take heart! Comparing Olynyk to Bargs at the same age, Olynyk is a significantly more effective offensive player- a better passer, better 2-point shooter, and better finisher. He's also a much, much better rebounder.
In his mid-twenties, the popular opinion on Bargnani was that he could be a star if he didn't play so soft and if he worked to score more in the paint. So far, Olynyk appears to share all of young Bargnani's assets without sharing his flaws. That's something to be excited about.