Brioni, Dunhill, etc. has great shirts but the problem is they're not as versatile and is better reserved for dressed up, really tailored suits.
This season, the shirts by Y's have gotten a lot more slim and have nice details. The shirts I tried on the other day are almost on par with DH shirts for slimness, they really hug the figure. I also dig the collar of Y's shirts which is relaxed yet still frames the face in a nice way.
Dolce & Gabbana seems to have nice plain shirts that can be dressed up or down but I can't find any around here, they only have the weird, loud shirts.