Every course they play a major at is a great course. Some courses are just a cut above though. What year, in your opinion, had the 4 greatest courses in major competition.

2000 comes to mind with Augusta (captain obvious here), Pebble Beach, St. Andrews, and Valhalla. Not only that, but Tiger dominated that year, making it that much cooler.

In 2010, however, it's Augusta, Pebble Beach, St. Andrews, and the great new course, Whistling Straits. I think Whistling Straits is a cut above Valhalla as a course. Great lakeside views along the shores of Lake Michigan, great Pete Dye strategy on every hole. The course is a monster and really makes you play at the top of your game. Valhalla is a great PGA Championship course. Birdies can be made, but not a ton of holes that have the "shock and awe" factor like the other courses already mentioned. Whistling Straits is almost a US Open type course that the PGA locked up as a mainstay in its Midwest course rotation with other future events such as the 2015 PGA Championship and the 2020 Ryder Cup, to go along with the 2004 PGA Championship and the already mentioned 2010 PGA Championship.

Any other years like these that come to mind?

2005 sites: Augusta, Pinehurst, Old Course, Baltusrol

It's hard to beat 2000:
Augusta, Pebble Beach, St Andrews, Valhalla.

Anytime you get Pebble Beach and St Andrews hosting their respective Open's, you know it's going to be special.

Gotta be 2010, with Whistling Straits being one of my favorites. Still haven't played there though...
And with Pebble, Augusta and St. Andrews in the mix, what more can you ask for?

As far as best goes.....I'd probably have to put my vote in for the 2000 lineup of courses.

I gotta say though, last year (07) had to rank up there as one of the highest in terms of most difficult courses....especially with the 1-2 punch of Oakmont and Carnoustie