Inquiring Minds Want to Know: Best Discontinued Set of the Last 10 Years?

I'm genuinely curious what everyone thinks about this. There have been a lot of cards released by a lot of companies since 2001, and many sets/brands that were short lived. What has been the best?

Are you a Masterpieces person? Goudey? Fleer Greats of the Game? Topps Gallery? There are countless options.

(PLEASE don't be limited to the couple I've listed here)

I ask because I'm pretty sure that I know the answer. Let me know what set(s) you've loved and lost and I'll show you my favorite later tonight.

Here's a hint: