Well, I think it's pretty established that I love this series to death, so I'm opening a topic about it.
Reasons I like it:
1. Characters
Galactik Football is really good in character building, most main characters have a nice and deep past, and almost all named characters are nicely well-rounded. (While leaving plenty of room for interpretation). There are also nice and intricate character arcs (My favorite being that of Harris. Going from nervous and cowardly henchmen of the big bad, to a devious traitor who gives Starscream a run for his money by actually succeeding
Without anyone noticing he's even on the 'wrong side'. (There are also signs he's going insane, always cool))
2. Animation
The 2-D animation leaves much to be desired, I admit, but the real action is in the pitch, where they use cell-shaded 3-Dimensional character models. While they re-use footage on a pretty large scale and except the Snow Kids, most Alien teams are obvious pallet swaps of the same model, (Budget restraints, I can imagine.). most used footage is AWESOME, and characters get about ten times more lively in their 3-D form. That, and the aliens used look extremely badass most of the time. (Rykers, Lightnings and Xenons FTW!)
3. Imaginative World
Even in 2-D, Galactik Football is a treat to watch, since they go at a pretty good length to make a colorful, imaginative galaxy. (While channeling Escher from time to time, AWESOME.), with pretty well tought-out alien races. Also nice is that they took the time to make you realise that, while not rare, humans are NOT the dominant species around here, and there's a huge variety of races walking around.
4. Ho Yay
So... much.... Ho Yay!
My inner slash fan is very pleased. Almost every male character has some subtext with another, and the fandom has established that Artegor is canonically in love with Aarch. (We're crazy like that)