Depending on the version of the song you put on .. Either as duet, trio, etc.. Seven Bridges Road is a good one to put on.. I'll even lipsynch one of the part's on that song... and get lucky too
OK, the last sentence is stretching it.
I don't know what type of version's are on CD-G allowing for duet parts, without one voice overlapping, if you just want examples of good male duo's..there are ton's..
Loggin's and Messina
Seals and Crofts-Ruby Jean and Billy Lee, and loads more
Simon and Gargoyle
you can get away doing anything by the "Association" with multiple male vocals
Cherish
Never my Love
depending on whether one can falsetto, or whether you want to trade part's ALOT of 60's and 70's R&B such as most songs from
Spinners
Stylistics
Delfonic
Climax-Precious and Few
Youngblood's- Get Together
and of course;
Seal's songs- He overdubs but still, several parts
Surface- The first time
Little River band
Lady
Reminiscing
Cool change...
Chicago
I've been Searching, Saturday in the Park
Wishing you were here, The things we said today
25 or 6 to 4, Feeling Stronger Everyday,
Happy Man
Some of Bachman Turner Overdrive
Bad Company has loads of stuff..
I have LOAD's if you really want more
Numerous Lenon and McCartney ballad's
Michelle
Yesterday
Norwegian wood
If I fell
I want to hold your hand
TON'S of beatles ballad's had two dominant voices
and last and least...something like Ebony and Ivory.... (blech)