It's only the coincidence of timing that makes the two films particularly comparable anyway, but on the scale of fictionalised memoirs of relative commoners marrying into 20th Century European Royalty and ultimately coming to a tragic end in a car accident (off screen) - and played by Australian actresses - this is much better than Diana. Not difficult, of course: Diana was mostly terrible but not terrible enough to have any fun with, mediocre more than anything else, but while Olivier Dahal's film does some genuinely bizarre things it's at least entertaining enough while doing them. Ignore the "inspired by actual events" caption at the start and treat it as a Danielle Steele miniseries for American television, because that's about the level it's playing on: a US primetime soap opera. (Dynasty even had an end-of-season cliffhanger when the whole family of oil barons jetted over to Madeupvania so the blonde daughter could marry a European Prince - and bride Catherine Oxenberg was actually related to Yugoslav royalty!)
Like Diana, Grace Of Monaco takes place after the fairytale wedding: Grace Kelly (Nicole Kidman) is no longer a Hollywood film star but an ordinary, though admittedly massively pampered, housewife and mother. She's feeling cast aside and ignored by Prince Rainier (Tim Roth), thinking about going back into acting (Hitchcock turns up to offer her the lead in Marnie) and her only real confidante is Frank Langella as a priest; meanwhile Charles De Gaulle and the boo-hiss French are planning to invade unless Monaco abandons its tax haven status and essentially bails France out after their Algerian wars...Robert Lindsay puts on a funny accent as Onassis, Paz Vega shows up as Maria Callas. There's a spy in the palace, a traitor, scheming relatives, gaggles of society harridans making a great show of their minimal humanitarian contributions; meanwhile Grace has to go to Protocol School to be educated in the ways of aristocratic conduct by Sir Derek Jacobi (that is how he's credited).
It's sumptuously mounted Sunday evening tosh of the first water and generally passes the time perfectly painlessly unless you take it at all seriously; and taking it seriously may be why it got booed at the Cannes Film Festival. (Alternatively it may have been booed because the French are quite plainly the bad guys, although these days it's tough to muster up much sympathy for tax havens.) There are strange touches such as Olivier Dahal's unaccountable predilection for holding Kidman's face in such merciless close-up you expect her breath to mist up the camera lens: I sat on the front row of the Cineworld Milton Keynes Delux Screen 9 and could practically count her nasal hairs and the blood vessels in her eyeballs. It's a bizarre choice and more distracting than anything else.
But in all honesty I didn't hate nearly as much as expected, given the almost global kick in the knackers it's had from the critics, and the idea that's the worst film of any year that includes Paranormal Activity: The Marked Ones or The Legend Of Hercules is frankly ridiculous. Treat it as a work of fiction (which from some accounts it is anyway) and it's an enjoyable enough, sometimes absurd, old-fashioned Hollywood costume frippery of the type they stopped making more than half a century ago. Far better than the disastrous Diana, it's almost certainly not going to be anyone's finest entry on their IMDb page, but I had enough of a good time with it. And any film in which someone turns up doing Alfred Hitchcock is fine by me.