I would like to second henrikegerman's suggestion of "Some Other Time" from the Leonard Bernstein, Comden and Green musical ON THE TOWN. This quartet is a gem, just exquisite with wonderful slightly complex harmonies. I would love the chance to sing the tenor line in this song. It was one of several numbers deleted from the movie version, alas. By all means, choose this.
"Why Stay/A Promise" from N2N isn't a traditional quartet number, but it has the 2 guys/2 girls you're looking for.
Also from Next to Normal is "Just Another Day," but that may be far too plot-specific for what you're looking for.
A few other 2 guys/2 girls songs from contemporary musicals that you may find worth looking into are:
"Not Alone" from A Very Potter Musical "Too Much Too Soon" from American Idiot "This Is How A Dream Comes True" from Shrek: The Musical "Any Minute" from 13
I'll second "Love Will See Us Through/You're Gonna Love Tomorrow." I would also suggest "Falling In Love With Someone (Quartet)" from Thoroughly Modern Millie and also "No One Is Alone" from Into The Woods. Be forewarned, the latter is mainly a duet for a majority of the number.