I've decided to use this thread as a place to post thoughts on Atlantis as I watch it, and would invite others to discuss the show with me here as well. I'm going to start by talking briefly about the main characters of the show, the premiere ('Rising'), and how the show is similar to and different from SG-1.
SG-1 vs. SGA: The similarities and differences
Because it's a spinoff, you'd automatically expect SGA to be similar to SG-1, and it certainly is in many respects. However, I noticed almost from the get-go that SGA has a more 'ensemble' feel to it. I also got a distinctly serialized procedural-esque vibe from the series premiere, Rising, as well, in contrast to SG-1, which is very much a Sci-Fi action adventure serial.
My thoughts on the characters
I really like the characters of Atlantis, both main and recurring. The main characters all feel familiar and very much evoke comparisons to their SG-1 counterparts, although they don't correspond to the characters you'd expect them to based on their individual roles. What do I mean? Here's an analysis of the main SGA characters with accompanying comparisons to their SG-1 counterparts:
Because she's the person in charge of the Atlantis expedition, you'd expect her to evoke comparisons to Generals Hammond and O'Neill, at least in terms of her role, but, instead, she evokes comparisons to Daniel Jackson due to her intellect and intuititive approach to things, something that is immediately apparent right from her introduction in Lost City and carried right on through to SGA.
Although he is very much the Jack O'Neill of SGA in terms of his role as the field commander for the Atlantis 'gate team', Sheppard actually reminds me more of Samantha Carter in that he's very much the 2iC when it comes to the Atlantis expedition as a whole. He's also very similar to Carter in terms of temperament.
Although it's not truly evident in his SG-1 appearances, McKay is very much the Jack O'Neill of the show when it comes to his temperament and status as the 'wit' of the show, although his role is very much to be a combination of Daniel Jackson and Samantha Carter as the 'brains' of the group, creating a very interesting character dynamic and dichotomy.
Teyla is clearly meant to be the 'Teal'c' of the show in that she's its 'resident alien', but she actually reminds me more of Sha're, particularly if you take into consideration the role that Sha're had in the original Stargate movie as opposed to her role in SG-1.
Aiden is really the only main character of SGA who doesn't have a direct counterpart from SG-1 in terms of his role, although he does remind me a little bit of Jonas Quinn.
My review of Rising
Rising is an episode that has to do a plethora of different things - introduce the main and major recurring characters; set up the premise of the series; serve as an introduction to the world of Stargate in case viewers tune in without having seen the Stargate movie or SG-1; and establish SGA as more than just a retread of SG-1 in a slightly different setting - and it could've been a massive convoluted mess if not handled and executed correctly.
Luckily, it doesn't collapse under its own weight because of the strength of the story it tells. The plot builds at just the right speed and we get enough information about each of the major characters to make them interesting while still leaving room for growth and development in future episodes. It also feels very much like a feature-length film in its structural narrative, and reminded me very much of the original Stargate movie.