End of season 8 (around when Logan returns, maybe a little before that) is arguably the strongest arc the show has imo. The problem is the first 14-16ish episodes are among the show's weakest.
Season 5 is my favorite season followed by 2 and then 1. I actually like season 4 a bunch though. Instead of 1 threat, they just keep moving onto new threats. Completely ridiculous but pretty enjoyable. It had some all time great Jack moments too, especially when he saves Audrey and Heller.
6 is my least favorite despite a strong first 4 episodes and my favorite fight of the series (Jack vs. Fayed).
Season 3 does get infinitely better when Saunders enters the picture as probably the show's best version of a dark mirror of Jack Bauer with a lot of lines that foreshadow Jack finally snapping in season 8.
I probably rank it 5, 2, 1, Live Another Day, 4, 3, 8, 7, 6.