Jodeci were such powerhouses too with K-Ci & Jojo. This is why I didn't outright say Boyz II Men is THE best vocally even though I'd say I ultimately prefer them. Boyz II Men and even Dru Hill just hit emotional nerves in me like no other groups, personally. Love me some Jodeci though.
More dance than R&B but a class 90s tune nonetheless. Most of my faves have already been posted, Return of the Mack is a beast of a song.
There are plenty of great dance tracks in the 90's R&B. Poison by Bell Biv Devoe, Hold On by En Vogue, Motown Philly by Boyz II Men, She's Got That Vibe by R. Kelly/P.A. are quality R&B dance songs. That style is often called New Jack Swing.