I wouldn't say there's ever been a time when Allen's films routinely made the top 10 -- he's always managed to release a total flop here and there to break up the streak -- but it certainly used to occur much more frequently than it does now. Manhattan opened at #1 in 1979, possibly the only Allen film ever to do so. (I can't find specific weekend data on Annie Hall, which is the only other likely candidate.) Various others have spent at least a couple weekends in the top 10. Still, no Allen film has ever been what you'd call a "blockbuster." His biggest hit, Hannah and Her Sisters (1986), made $40 million and never got higher than 5th place at the box office. Granted, if you adjust for inflation, Annie Hall's $38 million would be about $120 million today, and that would be considered fantastic for a low-budget indie. But it's still not commensurate with how beloved and acclaimed Allen is.
Consider this: Woody Allen has directed 38 theatrical features. The Dark Knight has made more money than all 38 of them combined. Isn't it strange that one of the most iconic American filmmakers of all time can barely scrape together a crowd to actually watch his movies? Then again, maybe that's only true in the United States. All of these statistics represent the domestic box office. Allen's films routinely do much better overseas, particularly in France, Italy, and Spain. (Or at least the more recent ones do. Box Office Mojo's foreign records only go back about a decade.) For example, Cassandra's Dream was a bomb in the U.S., earning less than a million dollars, but it made $21.1 million overseas. Match Point earned $23.2 million here, and another $62.2 million elsewhere.
We should also remember that Allen's films don't play on 3,000 screens, so it would be unrealistic to expect them to have $20 million opening weekends. The widest release ever for an Allen movie was the 1,033 screens devoted to Anything Else (2003), which opened in 12th place (so close!) and which was -- let us not forget -- a lousy movie.
Which brings us to the element that might make the most difference when it comes to Allen's box-office success: quality. Most people agree that Allen went through a creative slump for a while, and it's just been in the last few years that he's started to come out of it. The box office clearly is not a meritocracy -- terrible movies make shloads of money all the time -- but producing something good will generally improve your chances. Luckily, even if blockbuster success continues to elude him, it would seem Woody Allen is going to keep making movies anyway -- and for those who love his work, that's fine with us.
[Thanks to Box Office Mojo's indispensable records, particularly the page devoted to Woody Allen specifically.]