Update: commenter Hugh, below, notes that SciFi didn't actually cancel the series, but that it was cancelled by MGM, presumably because of production costs, especially as the US and Canadian dollar have reached nearly equal value over the years. Hugh postulates that SciFi was likely the only partner to be sorry to see the show cancelled. Seems plausible to me.
Update 2: despite some very interesting comments below, it appears that the Stargate franchise will live on, and on SciFi, via Universe. The way James Hibberd is reporting this, Universe will air on SciFi, and not on MGM's new channel as postulated in the comments. And SciFi is issuing press releases about this, so it appears the plan is for Universe to air on SciFi.
It ran a little long for a comment, but a couple of you have e-mailed asking about the cancellation and my thoughts and commenter Outlander chimed in here chimed in here with some thoughts as well.
I'm sad to say that I agreed with Maureen Ryan's assessment pretty much 100%. Sad because although I agree with her, it would be no skin off my back if they kept the show on the air and somehow figured out how to improve it. But I definitely agree that show had been waning, but unlike Ryan, I kept slogging through anyway.
The season four finale held a lot of promise and I found it a particularly good episode. But that episode focused almost exclusively on Rodney McKay and Sheppard, and those were my favorite characters. I always thought Joe Flanigan and David Hewlett who portray those characters were the best part of the show.
Last Friday's episode, which could've been interesting in theory wound up boring, predictable. I muddled through it last weekend and at the end thought, "this show is running on fumes now, such a shame."
Outlander brought up (in the comments) the notion of its ratings being the same as last year and being better than the ratings for Eureka and speculates the show may have done better on a different night. But I still think all things considered cancellation is a good call on SciFi's part. First, there will undoubtedly be more "direct-to-DVD" movies, form both SG1 and Atlantis sooner or later, so it won't shrivel up completely. Secondly, whether it happens now, or years down the road, it seems like ultimately somebody somewhere will take another crack at the Stargate premise, whether it's on SciFi or not.
I'm not privy to the production costs, but even though the show is produced in Canada, one thing I am pretty sure of: production costs for year five are greater than production costs for year one. So it seems likely, looking at it purely from business perspective that it was costing more money to produce something that wasn't correspondingly making more money.
I think because of the (relative) success of Battlestar Galactica, SciFi thinks:
a.) Between good shows and DVRs, shows can have success on Friday nights.
b.) That it ought to focus on producing shows which have *growth* potential
The fact is, Stargate Atlantis is stagnant, both as a show and in terms of ratings. Season five will get its full run, and there are plans for a two hour movie, so hopefully they will get to wrap up this installment nicely, as SG1 kind of did. I view the two part Moebius finale from season 8 as the SG1 finale, and it was a fitting end. Seasons nine and ten were another series really, they just didn't change the name to "SG1: It's Not Quite as Good Without O'Neill, But You'll Still Watch Anyway".
Please note, I am not bashing the creators, writers, actors, directors and producers of SG1 and Atlantis at all. I thank them for more than a decade of entertainment, at least 80% of it was enjoyed very much.