Here's a couple of songs, they're all personal favorites of mine. Mind, I'm not an R&B fan at all, so you just might like them as well.
Automatic (live) - A song from the debut album First Love; however, this live rendition is sublime.
Colors - A more recent song, brilliant.
Final distance - Beautiful ballad.
Hikari - The theme song for Kingdom Hearts (there's also an English version, 'Simple and clean'), awesome.
Letters - Brilliant song.
Traveling - Genius, upbeat.