Ali didn't try too hard nor had to that night. Jimmy knew how to land a right hand on Ali from their long gym association and it made the night a little interesting, the only time Angelo wasn't in his corner in favor of Ellis which was an oddity. Angelo said after the bout that he thought Jimmy had a chance until the big right hand hurt him badly but it was only because Ali was on 50% power.
As others have said, it wasn't Ali's most complete or exihilerating performance, but considering the solid credentials Ellis had (especially dominant wins over Martin and Quarry) it has to be one of the more impressive first fights back from a maiden defeat by a heavyweight champion in history. Certainly a more impressive win than the mismatches Lewis, Tyson, Bowe, Frazier, and Foreman staged to get their legs back after losing for the first time. This is much to Patterson's thrilling revenge win over Ingo or Louis' chilling demolition of Sharkey than any of the others mentioned. Not Ali's best performance or his biggest scalp, but the context of the win is somewhat impressive because it underscores Ali's amazing competitive drive.
One of Ali's better post-exile perfomances. Behind Foreman, the Frazier fights, Norton II and Quarry II. Ellis had all the makings of being a tricky opponent. Technical, cunning counter-punchers had troubled Ali earlier (primarily Jones, but also Folley) and Ellis also knew Ali very well. Still Ali didn't give him much of a look-in and became the second only to stop him at HW.