Personally,
any breast size is fine with me, so long as it is not too over the top when it comes to size. While I prefer the larger end of the spectrum, as seen in the two images below (
Lucy Heartfilia and
Erza Scarlet) and in my avatar (
Katsuragi), anything larger than that is bigger than I prefer. The largest bust size that I could tolerate for anime and/or hentai girls is the breast size of
Astraea (
Heaven's Lost Property). Anything bigger than that is just too much for me.
The Size I Prefer:
The Absolute Limit: