Speaking of which, Summer definitely underrated not in a Big Star kind of way (she's not forgotten in any way and I think even had a Broadway musical based on her songs like the way more popular ABBA did), but more in a she's an inner-circle Hall of Famer for her '77-'81 run of albums and should've had Bee Gees-level sales for those years versus the mere multi-platinum. Only P-Funk was better than her during her prime years for dance/funk/R&B music (Stevie Wonder took himself out of commission during that time).
Anyways, that was my rant. Best song of I'm A Rainbow is Highway Runner (which was included on Fast Times At Ridgemont High soundtrack, haven't seen that movie in 2 decades so don't remember what scene it was in if at all). That song's futuristic sounding like I Feel Love but unlike that song, has actual non-repetitive and redundant hooks. Brooklyn reminds me of Stevie Wonder's Isn't She Lovely in being a song to her kid and is just as effortlessly melodic.
Grades for her discography:
Love To Love You Baby B (1 great side-long track and 5 meh side 2 tracks. Not a 2112-level classic)
A Love Trilogy B+ (repeats the format of last album with 1 great side-long, Try Me I Know We Can Make It, that's even better than the more famous Love to Love You Baby, and 4 regular-length side 2 tracks of which 1 of them is a Barry Manilow cover which she made into a hell of a song, Could It Be Magic)
Four Seasons of Love B- (her 1st concept album 'cept the songs are meh, probably enjoyed more on quaaludes or whatever the #### the beautiful people in the 70s took in clubs)
I Remember Yesterday A- (now we're entering the start of the prime sheeit, has the hooks to match this time for an album that has concept of merging 40s jazz club/Sinatra music with then-current disco, I Feel Love sounds better in context as album closer that's supposed to signify a break with past...to music of future. Overrated as a stand-alone single)
Once Upon A Time A- (her 1st double LP, takes 3 or 4 listens to fully get, but worth it. Futuristic Cinderella-story concept)
Bad Girls A+ (side 3's meh, that just means the other 3 sides of the double LP are Olympian. A level above the same year's Off The Wall. I'm not the only one to say this is White Album/Blonde of Blonde of dance music...at least I would like to think.)
On The Radio A+ (a compilation but deservedly one of the more famous ones of anyone ever plus it has 5 A/A+ level songs specific to that compilation and only available on singles/live album otherwise. Doesn't get much better than those 5 songs, On The Radio/Heaven Knows/Last Dance/MacArthur Park/No More Tears, either.)
The Wanderer A (underrated in it's time (only certified gold) cuz' of the artists associated with disco backlash specific to 1980. Summer herself changed direction after peak of Bad Girls/On the Radio and went more new wave in exploring direction of the immortal rock-oriented track 1 Hot Stuff off Bad Girls but for a whole album!)
I'm A Rainbow A+
Donna Summer B- (This is the album Geffen convinced her to do with Quincy Jones instead of the shelved I'm A Rainbow. Like the 2011 Philly Eagles, a very awkward all-star team that's way less than sum of its parts (check out the credits of who's on album))
She Works Hard For The Money C+ (The title track has deservedly lived on and Unconditional Love a great secondary single...should've just kept it at that. After this her remaining 5 albums jumped off cliff into generica.)