Board Thread:Geometry Dash Gameplay Discussion/@comment-28743333-20160322200216/@comment-30249349-20180127023301

For me its

(Adapted to the user star system)

Stereo Madness: Easy 2 Stars

Back on Track: Easy 2 Stars

Polargeist: Easy 2 Stars

Dry Out: Easy 2 Stars

Base After Base: Normal 3 Stars

Can't Let Go: Hard 4 Stars

Jumper: Hard 4 Stars

Time Machine: Hard 4 Stars

Cycles: Harder 6 Stars

xStep: Hard 5 Stars

Clutterfunk: Harder 6 Stars

ToE: Harder 6 Stars

Electroman Adventures: Harder 6 Stars

Clubstep: Easy Demon 10 Stars

Electrodynamix: Easy Demon 10 Stars

Hexagon Force: Insane 8 Stars

Blast Processing: Hard 5 Stars

ToE 2: Medium Demon 10 Stars

Geometrical Dominator: Harder 6 Stars

Deadlocked: Medium Demon 10 Stars

Fingerdash: Insane 8 Stars

For all the Harder 6 Stars levels, their difficulty are pretty close. Here are all of the 6 Star levels (IMO) put in order from easiest to hardest:

Cycles,   Geometrical Dominator, Clutterfunk, ToE, Electroman Adventures