For me:
Prior generation:
OJ Anderson
Chuck Foreman
Pete Banazek
Modern era:
Edgerin James
Clinton Portis
Willis McGahee
Frank Gore
Duke Johnson
Duke gained more yards than all of them despite playing only 3 years. McGahee had a phenomenal final year, Heisman finalist. Portis lead us to a National Championship. Edge gained 296 yards against UCLA, marking the return of the Canes under Butch. He also starred with the Colts and could make the Hall of Fame. OJ Anderson became NFL rookie of the year and a perennial all pro. Foreman starred with the Fran Tarkenton Vikings. Banazek was a stalwart on the legendary Raiders teams of the 60's playing with two other Cane greats, Jim Otto and Ted Hendricks.
In terms of sheer talent, however, I agree that the pre injury Gore was the greatest Cane RB talent of all time. His vision, balance, toughness, speed, pass catching and pass blocking abilities were unparalleled. I recall seeing his high school recruiting film highlights. On a mediocre Coral Gables team, he set the Dade County rushing record. Running mainly between the tackles, he was near unstoppable.
Frank is still doing it at age 33. What a player.