I wouldn't place too much value in those metacritic ratings, I mean I think SGU started off with something crazy.
Yes, this show is freakin awesome. Ok, will try to attempt an objective look at things:
The first season involves the show finding its footing and giving subtle hints of a longer arc involving some conflict to come. It's more episodic initially with some team-building aspects and character discoveries that are relevant with subtle hints of the bigger plot arc and the enemy slightly. Very episodic.
The second season delves into things further and you find out things that hint towards this massive plot arc. There are various plot arcs intertwined but they all seem to indicate that they all come together somehow in the future. You find out more about the enemy and how it all sort of started. Actions in the past having drastic effects. Becomes more serialized.
The third season is the season where all the fans just went sort of nuts. By that, I mean they couldn't believe how great it got. Of course this doesn't do anything for you so here goes. You get back and forth episodes between the enemy and the good guys. However, you start to question if the enemy is really the enemy? Are they only trying to save themselves? In this season, you also get this mythological/historical aspect to the show in the background. Heavily serialized, thick storytelling.
Overall, I'd say imagine the initial good seasons of Alias and Lost where things seem to be building up but done in X-Files fashion, sort of. The set up for the massive plots they have are similar to the introduction of the Shadow in Babylon 5. Not an introduction to the enemy, just a sort of buildup of lots of things coming together that you have no idea what will happen next. It ties in some bits of myth/history, current character dilemmas/situations, characters that you appreciate and root for, questionable enemies, uncertainty about how it'll end, great amounts of humour, shades of gray, storytelling can get really dark at times, and coalescing mini-plots into this giant uncertain plot.
I know this might seem like a glowing review but I'll do some bad points too: the first season is kinda too episodic and might turn you off initially but just imagine this to be like the first season of Babylon 5, kinda introducing the players and slight hints of things to come. Don't expect completely accurate science in this, it's more popular science stuff. But this is to be expected with all sci-fi shows. There is a slight gross factor involved, there are some things that are yucky. I can't think of any more right now but think that's just my fandom preventing me.
Hope that helps.
