I almost ran "Necropolis" but decided against it for this reason:
Although it is big and has a cool alt.ranger and some neat monsters, it also had various nonsensical traps and such that operated something like this:
"If your PCs touch the doorknob on the left and say the magic word, they make it through to the other side. If they touch the doorknob on the right, they are instantly transported to the 666th plane of the Abyss where they die instantly. No save."
-- or --
"If your PCs stand on their head and say a magic word [which has nowhere been revealed] they avoid dropping two levels from a magical ray that automatically hits. No save."
I am making these examples up, but I am hardly exaggerating. Its a wierd adventure in that it contains many elements that appear designed to reinforce the supremacy of the DM at the expense of player ingenuity. I think Gygax wrote it a while ago because it strikes me as being a bit immature. Of course, maybe I just like adventures where a smart group of PCs can reason their way out of tight spots. Without actually having played Necropolis, it just didn't seem like that type of adventure.
So go for the Banewarrens or one of Monte Cook's masterpieces. I really liked "The Heart of Nightfang Spire" for a dungeon crawl.