In my opinion it goes in the order they occur. Season 1 easily being the best. Probably the best thing i've ever seen on television, closely followed by The Shield Season 5. Pretty much everything about this season works. As said before the crisis is more personal and you actually feel like you have some investment in the characters. They also actually follow the real time format pretty well here. Season 2 is pretty close to season 1 quality for the first 12 or so episodes, then it somewhat falls apart but is still better than pretty much any 24 to come. Season 3 is overall average. There are some really great episodes about a third of the way through but the last few arent too great (Note to OP, when you get to season 3's finale make sure you check out the deleted scenes. It makes the finale so much better. It seems like they shot it hoping for a full 60 minutes and then found out they only had 42 and had to scrap some important stuff.) Season 4 starts off great. The first 8 episodes are back to season 1/2 form, then they get into the rehashing of previous storylines and everything just feels like you've seen it before. This is where 24 takes a huge nosedive in quality and oddly enough when it becomes increasingly popular. Season 5 is just a complete suckfest. Some of the worst television i have ever seen. Entertaining if you are just looking to watch a kind of rediculous, unbelievable, turn your brain off straight to video action movie. This is the season where they tried mainstreaming 24. They made it so that if you missed a few episodes no big deal. They made the show for the casual viewer. Season 6 I have only watch half of because of my hatred for Season 5. I decided to give up on a show that was once my favorite show and one that i recommended to everyone i knew. I decided to just watch season 6 in 2 blocks of 12 straight through. That way if an episode sucked i'd only have to wait 42 mins for a new one. So far season 6 is much better than 5 and the majority of 4. Maybe thats because i've just accepted now that 24 is a low quality action show or maybe it's because of watching it non stop, back to back episodes. So this is how i'd put them.

S1
S2
S3
S4
S6 (first 12 ep)
S5

I'd recommend that you just stop watching the show at the season 3 finale. It's the best point to reach some closure of previous stories and get out of the show while it's still good. Now i'm sure you're not going to be able to do that because you'll just have to know what happens next, but if you're anything like me you'll regret it. These last few seasons have ruined what was once a great show.

1. Season 5
2. Season 1
3. Season 2
4. Season 4
5. Season 3
6. Season 6

I've seen it referenced before quite a bit in the past as one of the more outlandish events in 24, though it's probably been topped frequently in later seasons. I was probably exaggerating by saying "most infamously" in my original post, since I don't hear it mentioned as much now.

Best - 4 - 5 - 1 - 2 - 3 - 6 - Worst

Frankly: 1, 2, 3, 4, 5, 6

It's not so much a long, slow decline in quality as it is a gradual decline until halfway through season 4, followed by a steep plummet.

IMO - 1,4,5,2 (first half was good then it went downhill),3, and 6 (stopped watching several weeks ago).

1
3
2
5
6
4

3>1>2>5>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>4

Only saw the first 4 eps of this season before I fell behind. Now I have to wait for an actual summer run or more likely the DVD.

I actually gave up after about episode 6 or 7 of this season, but part of that was because Heroes is so much better. I doubt I'll even watch the rest of this season on DVD.

I think season 5 of 24 is the best of any TV show I've ever seen, w/ the exception of Buffy season 5, which is about equal to it.

As a hardcore fan who has been watching obsessively since the pilot episode, my rankings are as follows:

5
1
2
4
3
.
.
.
.
.
.
.
.
.
.
.
.
6 (the current season is when I started to lose interest)

Let me put it this way - good or bad, I blew through seasons 1 - 5 without batting an eye, whereas I have the last 5 episode of season 6 sitting in my Tivo, unwatched, with no real desire to watch them...