Gogol's Key Works

From Cambridge History of Russian Literature (1992), p.166 on:

Nikolay Gogol (1809-52)

- Ganz Kuechelgarten, idyll(1829)

- The Hetman (Getman), A chapter of an unfinished historical novel (1831)

- Evenings on a Farm Near Dikanka, collection of eight stories (1831-2), including "Ivan Fyodorovich Shponka and His Aunt"

- Mirgorod (1835), story collection, including "Viy," "Old World Landowners," "The Tale of Ivan Ivanovich Quarreled with Ivan Nikiforovich"

- Taras Bulba, psuedo-historical novel (1835, rework 1842)

- Arabesques, collection of essays and stories (1835), including "Nevsky Prospect," "Diary of a Madman," "Portrait" (this last reworked and republished in 1842) (these 3 part of the St. Petersburg cycle)

- "The Nose" (1836) (the 4th of the St. Petersburg cycle) 

- The Inspector General, play (1836)

- "The Overcoat," the most famous of all his stories (1842) (the last of the St. Petersburg cycle)

- "Rome", fragment from projected novel Annunciata (1842)

- Dead Souls, Part I, novel (1842)

- Selected Passages from Correspondence with Friends (1847)

- Dead Souls, Part II, novel, fragments (1855, posthumous)

So, according to this Cambridge History, the most worthy works of Gogol are 1) The five stories of the St. Petersburg cycle; 2) The play The Inspector General; 3) The novel Dead Souls, Part I. Marked above in bold.