Maggie Smith is riding the crest of another wave of recognition in an immaculate career thanks to “Downton Abbey.” Kevin Kline, on the other hand, only seems to work when he enjoys it. Their connection in “My Old Lady” is uncommon: Kline has inherited from his father a massive apartment in Paris, while Smith is its tenant. Thanks to an arcane French real estate standard called viager, he must pay her every month, in what amounts to a reverse mortgage. She’s 90 … but isn’t dying anytime soon. This film should be a broader comedy than it is, and it should also come much closer to realizing the abilities of its talent than squandering it. There are some comedies that should actually concentrate less on the intricacies of the story and go with what works. “My Old Lady” is almost worth watching because of its stars, but not quite.