Steffi might have had more rivals (Seles,Navartilova,Sanzchez Vicriao, Martinez, Zvereva, Hingis, M.J. Ferandez) Just to name a few. I always loved watching justine and kim, don't know why
I think because their games were so different, and it was interesting to see who would come out on top (except in slam finals). Obviously, that was back in their first careers.
The OP has listed some great matchups, and I'll reiterate a few.
Venus vs Serena, classic, even if people complained.
Venus vs Davenport, classic battle
Davenport vs Serena
Elena D. vs Serena
Aga is almost always interesting to me, except when she plays Woz, that's always a thumbs down.
Myskina always gave you good bang for your buck. Can't think of a particular matchup, but I would probably watch most of her matches (I will never watch her Olympics one ever again, though
Vera Z vs. Vera Z.
Amelie vs Hingis