I also have to nominate:
HL2 Ep2 the house seige, when you are driving, and get trapped by the laser barriers.
That was intense!

Crap, I forgot about Siren. Just about the most terrifying game I've ever played. The highlight for me was "Reiko Takato, Day 1, 02:00, Hanuda Elementary School"--the one where you're an elementary school teacher trying to lead a student out of a shibito (sort of but not quite zombies)-infested school without any way of defending yourself (at least not for the first two thirds of the level). After a while, my nerves were so shot that I just had to lock myself (well, my character) in the bathroom for ten minutes before moving on.
The game as a whole does some interesting things with level design. You'll be going through the same nine or so areas several times, but as the shibito establish themselves, they start rebuilding the village in unnerving ways, so things get stranger and stranger on each visit.
So, I guess you could consider this entry number eleven on my list.

Sheesh, what's wrong with me... I'm supposed to be a Sonic fan. How could I forget about Star Light Zone...?
Another level in a Sonic game I found memorable for the same reasons you praised Star Light Zone for, was the serene IceCap zone in Sonic 3 (whose track was rumored to have been composed by Michael Jackson).

Lets see if I can think of some.
Dark Forces: Probably the first level in the game, because I played it so many times in the demo before i ever had enough money to buy the game.
Dark Forces 2 Jedi Knight: Besides the boss battles it's got to be the level aboard the crashing ship near the end of the game. and the fact that finding all the secrets in each lvl actually gave you something usefull (force points)
Fallout: Junktown and Adamantium Boneyard... although the Glow rocks also.
Fallout 2: Vault City and Gecko, as well as the Sierra Army Dept.
Half Life 2: Ravenholm was definatly memerable, though my first time through I HATED it so much, ran out of ammo and could never seem to keep the saw blades long enough.
Probably the opening levels for both Crusader: no regret and no remorse played them alot on the demos as well. Been a looooonnng time since i played those.
Tie Fighter: Basically the whole game was AWESOME!
Favorite quote from Portal: "Remember that time I was like it's time for you to die and you were like 'noooooo'" I think it wen't something like that LOL haven't played it recently.
I'm sure there are more I will remember later but thats it for now

For me:
The first level after the part where you drop down from that spacecraft/plane thing a ma jig! For that time MDK was AMAZING!
The first time you hear the Zelda tune on the black and white Gameboy.
The frist time you can walk freely in Zelda: Ocarina of Time on the N64!
Tie Fighter indeed!! THE BEST SPACESIM!!
The frist time you meet Glotis in Grim Fandango
Half Life 1 the Tram/Intro Part! ( Same goes for Half Life 2! )
Resident Evil: Code Veronica on the DC! AMAZING 3D!

NO MAX NO, PLEASE, I DIDN'T MEAN TO!
Trick or Treat!
- [url=http://www.youtube.com/watch?v=CXR6jDISwdA]Archades (when SquareEnix does a megalopolis, it does it good)
Did I just destroy a whole battleship with a giant-ass laser cannon? HELL YEAH!
That's off the top of my head, there are many more....

The most memorable level in a game? The Omaha beach level in Medal of Honor: Allied Assaunt.
I didn't really care much for the rest of the game, but that level was incredible!