I've got it!
It's probably the toys and the fiction for me.
The toys are honestly amazing. They're two/three-plus toys in one, meaning that you can do anything with them. You can smash stuff with a tank and then make a giant robot stomp over the ruins without having to run back and get another toy. They're like a Rubik's cube, too, only solvable.
I like seeing what stories they can tell with the characters, and often they're amazing (Beast Wars and Animated spring to mind), and they're imaginative. Plus, how can you not love the fact that your favourite characters are guaranteed to have toy versions?![]()