Bay is ok as an action director, but thats about the extent of his abilities imo. I really didnt care for Transformers 2 in all actuallity, although the special effects were spot on.
Eastwood and Scorcesi (spelling?) are my top directors at the moment. As well as whoever directed Casino Royale. They tend to bring out more dynamics and intracies of the characters and the plots.
But thats just my perspective. While I like the occasional action movie, I need something a bit more deep and thought provoking. Miyazaki also is a great director, as is Shirow Masumane. (6 years of art school must have warpped my fragile mind lol).