It is a matter of taste, as many posters have already stated. Many North American chains serve very weak espresso drinks, or even worse to me flavoured coffees, which don't appeal to tastebuds used to something else.

Tchibo had been serving decent coffee and espresso drinks long before it became popular in North America, but I would put Illy well above them for a chain. For UK chains already mentioned are Pret (not the US version however), Costa, and I will add Apostrophe. There are many chains I enjoy, but very few North American ones I like. Hence I tend to see out micro-chains or independents in North America, as they often serve stronger espresso drinks and better quality coffee.

I'm adding Edinburgh's Chocolate Soup to my list as well - somewhat inconsistent in service but when they are good, they are very good. And the location gives them extra points (albeit it by yet another Starbucks)

And edited again to add Julius Meinl which counts as a decent chain.