For me, I always thought 2's level design was annoying. I go one way, and come back the other.
The bosses in Advance 3 are pretty darn sweet too.
And Advance 3 presents the most opportunity for challenge.
Advance, well, I'll have to say one thing about it.
Up to Egg Rocket, the levels are breezy.
Egg Rocket is a big headache,
Cosmic Angel has an annoying boss,
and the X zone is my biggest migraine.