I dunno about best, but I think Phantasy Star Zero deserves a mention.

Pixel-Perfect

I agree.

or Ketsui Death Label for managing an incredible amount of on-screen sprites without crashing the DS.

pills4louis

I also agree.

I love the graphics in Soma Bringer, they look beatifully hand drawn, they reminded me of Legend of Mana. I also loved the detail and quality in the backgrounds and sprites in SMT Devil Survivor. Didn't love many of the demon illustrations, though.