"Notting Hill" was written by Richard Curtis, who wrote and directed "Love Actually". (Richard also wrote "Four Weddings and a Funeral", as well as TV's "Black Adder" and "Mr. Bean". He's one of my favorites.)
"Definitely, Maybe" is written and directed by Adam Brooks (who brought us "Practical Magic" and "Wimbledon"). To my mind, he's a pale imitation. Your mileage may vary.
Now, "the makers of" might be technically accurate -- those three movies were each paid for by the same corporation, after all. But as a branding issue, is it really fair to suggest that the viewer can expect the same level of quality?
Maybe it is. I don't know.
But I still insist that creative teams are neither equivalent nor interchangeable.
If I were Richard Curtis, I would be insulted.
If I were Adam Brooks, I would be insulted.
If I were a movie-going consumer, I would be insulted.