There's generally a 2-3 year lag between when a title gets published in Japan and when it gets published in the U.S. Not all titles get translated, which also makes collecting manga a challenge. There are a number of Japanese manga awards out there and here are some titles owned by the library that have won these awards.

Thermae Romae by Mari Yamazaki won the Cartoon Grand Prize (a/k/a Manga Taisho) in 2010 for this story about a Roman architect who moves forward and back in time in his pursuit of the perfect bathhouse design.

One Piece: Romance Dawn for the New World by Eiichiro Oda won a Best Japan Cartoonist Award this May,

Cross Game by Mitsuru Adachi won a Shogakukan Manga Award for the shojo division in 2008.

Ooku by Fumi Yoshinaga won a Shogakukan Manga Award for the shonen division in 2010.