"More than 5 times"
I actually saw the movie 7 times in theaters, and I've watched it a bazillion times on DVD.
I would agree for the most part with X-Maniac.
Singer's films are technically better, but "X-Men: The Last Stand" is funner.
I think both directors succeeded in bringing particular elements to the table that the other failed at.
As far as "X-Men: The Last Stand" goes, my original opinion on it remains, 2 years later: When it succeeds, it is absolutely the best of the trilogy. In concept, it has the most epic ideas. In execution, it is lacking in many areas, and some ideas were absolutely horrible (killing Cyclops, curing Rogue, killing Xavier, turning Wolverine into a leader, Magneto regaining powers, Xavier "surviving" in the braindead body), and when the movie fails (and it does in areas), it's the worst of the trilogy.
So, Singer's films are much more consistent. They don't do anything horribly wrong, but they don't exactly reach the potential that the X-Men franchise has.
I think that Ratner's film reached the potential, but at the same time, did some things horribly, horribly wrong.
In the end, I love all 3 movies. I can watch any of them at any time, and as an X-Men fan, I am very satisfied with the overall trilogy. Except for a couple things, like the aforementioned flaws in X3, the lack of Gambit, and Nightcrawler's disappearance, there isn't much that I would do differently.