Lufia II's, on account that the level was like every other dungeon: filled with puzzles.

I'll agree with a couple of people on the Bloodlines sewer, that rocked. The vampire down there was actually scary.

Super Mario Bros (the whole F'ing thing)

Think about it, the game starts with Mario jumping down a sewer drain. The argument could be made that every level from that moment on takes place underground in a sewer... that or it's all a hallucinogenic acid trip inside the head of an Italian plumber who was consuming mushrooms while at work (but there's no time to explain that theory here).

This thread question has been answered. So now let's do the Mario!
https://www.youtube.com/watch?v=SRlEUdzDpB8

The first three leves in Eye of the Beholder take place in the sewers behind Waterdeep, and I think they are pretty awesome. And there are several sewer levels in Neverwinter Nights and I recall they're mostly fun.

I remember that Blood Rayne 2 and Heavy Metal F.A.K.K. 2 have sewer levels.

Also Half Life 2 has sewer parts trough the hole game and iI think the chapter before entering the citadel in the end was a complete sewer level.

I think one of the design decisions in Enter The Matrix that showed that the Washowski's were a little... naive was that OMG they actually even included a sewer level!
I think point was that they'd become such a cliché at that point it was laughable but I guess enough time has past that they can be respectable again

The Game of Thrones RPG has some pretty decent sewer-like levels that are fun enough but I think, in general sewer levels sink!

They need to make a realistic sewer level which isn't huge and spacious but tiny and crammed, and you are literally swimming through a bog of shit, contracting every disease under the sun as the poo splatters all over your face and in your eyes

...while fighting giant rats.

Seriously, when is that game coming to gog?! It's so much fun, and really makes up for the decidedly average movie

Deus Ex hat a decent sewer area with a nice surprise. Ive only found it on my third play through if i remember right, so i think it was entirely optional..

Gotta agree with Dishonored as well, i hated the clamshell things of course, but the areas themselves were fine.

Marathon 2 had several good sewer levels...

But yes in general, they're as overused as warehouses and office spaces, in shooters at least. I hate F.e.a.r :D

Was Baldur's Gate mentioned?

I'm probably the wrong person to ask since I never had an issue with sewer levels, but the short sewer missions in Shadowrun: Dragonfall weren't bad, especially the one with the time limit was interesting (although I usually despise time limits).

Planescape: Torment.

I remember playing it but I don't remember anything really outstanding about it... other than the giant boss at the end, that is :)
Weren't those catacombs, if we're talking about the same level?

The sewers in Postal 2 are unusually long: several thousands of kilometers. ;)