“Tower Heist” is an ensemble, and a strong one at that, led by Ben Stiller, Alan Alda, Matthew Broderick, Casey Affleck and Tea Leoni. But Brett Ratner’s blast of an action comedy truly brings out the best in Eddie Murphy, something many of us may have forgotten about. Fast-talking, flummoxed and full of false bravado, Murphy gives a performance as a low-level thief that recalls his signature work in the movies that made him a superstar in the mid-1980s — like “48 Hours” and “Beverly Hills Cop.” When Murphy’s on screen in his classic comic mode, it’s hard to focus on anyone or anything else. It’s as if we’ve turned back time and erased all those family-friendly duds and lame laughers that required him to climb into yet another fat suit or talk to even more animals.