SG1 is a great example of a show that has a great ending, and then was renewed like twice after it should have ended.

You’ll get like 3 or 4 good seasons out of Atlantis. It’s fun. The show runs into issues near the end with some poor writing and a main character dropping off. Although I loved the actors who came in later on, it wasn’t enough to resolve some bad plots. Worth a watch though, the show wraps nicely… unlike Stargate Universe…

Universe had promise, but it didn’t get a fair run. They also had a scene that pushed with one character death being a bit too much for me, which kind of fits with the realist / dark / edgy vibe they were going for. Worth a watch if you’re okay knowing it doesn’t have a real ending and want more universe building, otherwise skip it.

Skip the SG1 “movies” that come after the series.

There was a TV movie created (called origins?) that takes place decades before the series. I recall that being a fun watch.

Atlantis is cool, bad guys are actually threatening, the cast is fun, and the world building doesn't go of the rails as much as SG1 in the later seasons. It strikes a good balance between serious stakes and more light hearted space shenanigans.

Universe is... different. It's a very serious show, that clearly tried to have a tone similar to the Battlestar Galactica reboot. Sometimes it works, but it's hard to see where it was going (literally) before being cancelled.