What else could there be? The Surprise Song by The Jacksons comes into my mind, but you can only find it on YT.
"What's So Good About Good Bye" is a Jackson 5 song you can only find on "Motown Unreleased 1969", I forgot that one.
There are some songs without Michael's involvement (e.g. 2300 Jackson Street sessions) and Michael did backing vocals on a few songs for Stevie Wonder back at Motown. I don't count remixes or A Cappella versions etc. I believe that's it, but I would love to get information on more.
Those and:
- You've really got a hold on me (J5 version) - "On Motown sings Motown treasures" (1998)
- You've really got a hold on me (Bobby Taylor featuring the Jackson 5) - Also on "Motown Unreleased 1969" (1998) (but I'm not even sure if I hear MJ in this.)
- J5/Michael did backing on some Jermaine songs songs
- J5/Michael did backing on some Jackie solo songs (not 100% sure, should check)
- What's Your Game (song written by "the Jackson 5")
I was also thinking of things like
- Greatest hits (quadraphonic mix) (different from album version, some have slightly different lyrics)
- Hum Along and Dance (uncut)
- The Disc-o-Tech instrumentals
- Ask the Lonely (alternative version)
- The 1987 remixes, distinct from 25 Miles original version
- Farewell My Summer Love 1973 distinct from 1984 version
- various versions of the Steeltown tracks (I gave details earlier today in thread: https://www.mjjcommunity.com/threads/are-there-several-versions-of-the-steeltown-records.137409/ )
But maybe you don't want to count such alternative versions
Then I was thinking of unreleased, leaks and T.V. only stuff that you probably don't want to count.
(I may forget things.)