Rhodox’s (of Something Awful) Painterly Pack is out of this world in terms of content. Rhodox's website offers literally thousands of different variations of the Minecraft blocks, resulting in infinite combinations of texture packs for everyone to enjoy. He also provides artwork for a number of Minecraft mods, allowing you to keep your textures uniform. This isn't an example of quality vs. quantity though—there's real artwork in his texture pack. There are even holiday themes when you find yourself in a snowy biome and feel struck with the inspiration to build Santa's Workshop.
With the goal of making Minecraft look as realistic as possible, this mod certainly hits the mark. Using it with the GLSL shader mod will blow you away. You'll probably forget you're in a world where everything is a cube.
SMP is an old face in the Minecraft texture pack community, making a number of well loved packs. Over time, he's learned more and more about pixel art and he's left those old packs behind to make this one. Visually speaking, this pack is loaded with texture, and is reminiscent of other familiar packs while still standing out on it's own. It certainly helps that he has his own art collection for the pack too, which many others tend to leave out altogether.