rating the levels

S Tier:
Compton's Cookoff - fantastic concept, and so good at illustrating its themes that it makes about half of the other levels redundant, at least in part
The Motherlobe/Quarry/The Questionable Area - just dicking around in these areas are very fun, as it should be. lots of great optional dialog

A Tier:
Hollis' Classroom/ Hollis' Hot Streak - the structure of this part of the game, including the casino part, rules. depressing that they don't try for something this cool again until the very end, and it's not as good.
Strike City/ Cruller's Correspondence/ Ford's Follicles/ Tomb of the Sharkophogus - I've seen some people angry about the amount of Ford in the game but I thought this all tied together very well, and the levels all had cool gimmicks. Really felt bad each time I put a piece back together.
Cassie's Collection - very funny all the way through, and while it is yet another old Psychonaut (yaoP) it's actually about new things. still a little stale structurally, but that's an overall game problem and not its fault

B Tier:
Lucrecia's Lament/ Fatherland Follies - this section was probably supposed to be as cool as the Hollis part but they had to cut it down, still good stuff, overall satisfying ending.
Bob's Bottles - lot to love about this, but it would have been way better if it wasn't yaoP and if you didn't immediately cure his Alcoholism. if it was close to the same thing but a side character it's A or S teir: well written, looks good, plays interestingly
Loboto's Labyrinth - A fun opening, though I really thought Loboto would be more integral after all that

C Tier:
PSI King's Sensorium - I'm being meaner than I should be because it's just not an aesthetic that I like. I do feel like it should play weirder than it is, if it's gonna look that trippy, but it's pretty normal. Also angry that it hides that it's yaoP until it gets going.
Green Needle Gulch - It's fine, I miss running around the rest of the map tho

That's it, nothing worse than a C