It’s hilarious that, for her most famous role, they effectively said see, first, we’ll do our best to make you look unattractive as a woman in her forties – you know, the better to contrast with how good you’ll look after your life changes for the better. And then we’ll change your look again, doing you up as a rich guy’s trophy wife.
The gag, of course, being that she looked better in real life at fifty.
I prefer the formula of half the age plus 7. That gives me a target starting age of 41.
Kate Hudson is 38. Close enough.
Cameron Diaz and Carrie-Anne Moss are still rocking it, as are Gillian Anderson and Drew Barrymore.
And let’s not leave out a double-barreled helping of Jennifer: Aniston and Connelly.
Victoria Justice definitelly, real beauty! 
Take a look: http://www.imdb.com/name/nm1842439/
So proud of the Dopers lining up for Dana Delany, great taste here even in celebrity crushes! I thought I was the only one. Dana’s too old for me though and Carice Van Houten is too young by the strict 5-year rule (it would have been difficult for me to wish death on Carice’s husband Guy Pearce anyway…) so I’ll pick another babe with that “heiress who doesn’t mind going up to the cottage to drink beers” vibe:
Not to be a killjoy, but SMG is about 10 years too young for you, by the rules set up by the OP. It’s easy to find a crush when you include people way younger or older than you. For example, Scarlett Johansson melts me, and Kate Hudson is simply incandescent, but alas, I had to settle for Lea Thompson (Mine! Mine, i tell you!)
Do you have a backup not named Lea Thompson?
Benicio del Toro has one year on me. The Bestest Boyfriend kind’a looked like that - nobody would mistake them, but general looks, beginning with “no, I haven’t been in a fight, my eyes always look like this”, continuing with “last time anybody called me ‘pretty’ was my grandmother at my baptism”.
Ah yes… IMHO, the hotter Bruni sister.
Amy Adams is just beautiful, absolutely gorgeous, and is about my age.
Alyssa Milano was never someone I had a big crush on but she’s a baseball fan so she gets big points there, and she’s a year older than Amy Adams.
Jamie-Lee Curtis (a year younger than I am).
But I object to the term age appropriate (my wife is 15 years younger then I am… and we’ve been happily married for over 17 years).
Jensen Ackles is quite my age, a little younger I think. But as I go more with characters as with actors when it comes to TV shows the correct answer would be Dean Winchester.
You know, I never really noticed it before but Dana Delany looks quite like Diane Neal, almost uncannily so in some pictures. One is ten years older than me, one is ten years younger; can I take the average and crush on them both?
Ooh, it turns out that Gretchen Mol is 4 months older than I am. However, to my dismay, the delicious Lizzy Caplan is too young for me, clocking in at 9 years younger.
Kate Winslet for me. I also have a thing for Jenny McCarthy, Sofía Vergara and Cameron Dias.
Jennifer Aniston is the opposite. I find her repulsive for some reason.
jessica alba. yowza… 4 years younger, but close enough! Crush began with Dark Angel… so much tight leather!
Shhhh…she may not be aware of she’s hotter than her more famous sibling, and I know I’m way hotter than Sarko, which makes me think I have a real shot at making this crush happen. 
OP’s rules, but both at the same time is fun to think about.
Jeremy Irons, who’s seven weeks older than I am.
If I’m picking just one, not that long ago I would have said Jennifer Lawrence. But I honestly think Kristin Bell is the one. 3 years younger, I think that’s reasonable.
I forgot about Ming-Na Wen. Ming, I’m so sorry; please forgive me.
Bit surprised that there is only one vote for Ms Bellucci.
And none for Salma Hayek.
In fairness, neither woman fell within the parameters of the OP for me. 