Here are my picks:

Archon:
https://gamefaqs.akamaized.net/box/0/3/4/25034_front.jpg
Not only one of my favorite game covers, but the whole package was awesome! It reminds me of M. C. Escher. I'm not sure who illustrated this. If you want to see how awesome was the box inside, here's a video review I found on Yutube: https://www.youtube.com/watch?v=cR7gbM-lDr4

Maniac Mansion.
https://mixnmojo.com/galleries/full/full20071020150617.jpg
Illustrated by Ken Macklin. I love this one! That's how I imagine the characters, not like those deformed goofy designs from Day of the Tentacle (poor Bernard, what they did to you). Years ago I illustrated a cover based on this for a Halloween edition of a Venezuelan online comics website, it was fun to do.

Zak McKracken and the Alien Mindbenders.
https://gamefaqs.akamaized.net/box/5/1/1/25511_front.jpg
Illustrated by Steve Purcell, who created Sam and Max. Even though it's third on the list (I'm going chronologically), this may be my favorite of them all. I love it so much, it captures so well all the imaginative elements of the game. :) Very nice topic, I love cover art. That one from Another World is one of my favorites too. :) Love that game and the sequel, no doubt one of the best C64 games ever made. The cover art is very 80's indeed, love it! :)

Edited: typo.

Hehe, I had that game, and I subscribed to that magazine as well ;-)

Sorry, but it is mandatory that this be mentioned in every video game cover art thread:

http://www.joeredifer.com/crap/gaiaresUS.jpg

Daggerfall is probably my genuine favorite box art. The raised 3D feel to it, and the metallic finish. I remember buying the game on a whim from Babbages while on vacation in Florida. I read the manual cover to cover dreaming about playing the game until I was able to install it a few weeks later. It turned out to be one of my best purchases ever.

Nice retro art in that link. I love that stuff. I wouldn't completely knock off all the new ones, but I do agree that back then there was much more quality.

And more from me:

Wizardry: Knight of Diamonds

Wizardry: The Return of Werdna

Shin Megami Tensei

Double Dragon II: The Revenge (NES)

Dark Seed II

Ravenloft: Strahd's Possession

Nocturne

The Secret of Monkey Island

Alone in the Dark

Worlds of Ultima: The Savage Empire

Ima go with Snake Eater European cover, Americans kinda lost out on that one and got a kind of generic one.

https://upload.wikimedia.org/wikipedia/ru/thumb/1/1a/Metal_Gear_Solid_3.jpg/256px-Metal_Gear_Solid_3.jpg

Here's the other version;

https://upload.wikimedia.org/wikipedia/en/thumb/b/b3/Mgs3box.jpg/250px-Mgs3box.jpg

Vagrant Story;

https://images-na.ssl-images-amazon.com/images/I/61KPFN43GSL.jpg

Persona 3: FES

http://www.digitaldevildb.com/images/boxart/full/persona_3_fes/p3fes_basic_full.jpg

System Shock

Blackthorne

I've got that version, and yep it's awesome.

Ultima 3: Exodus: Totally metal.

http://www.mobygames.com/game/exodus-ultima-iii/cover-art/gameCoverId,2435/

Alien Breed: Derivative but striking.

http://www.mobygames.com/images/covers/l/103077-alien-breed-amiga-front-cover.jpg

Axis Assassin: Classic EA had so many really striking covers that aped music album art.

http://www.mobygames.com/images/covers/l/93748-axis-assassin-atari-8-bit-front-cover.jpg

Missile Command: Classic Atari games often had this interesting collage format.

http://www.mobygames.com/images/covers/l/108024-missile-command-atari-2600-front-cover.jpg

Agony: Can't be a cover art thread without Psygnosis. They had the same album cover idea that EA pioneered.

http://www.mobygames.com/images/covers/l/69591-agony-amiga-front-cover.jpg

Beamrider: Rare instance of a classic Activision cover that didn't have the cartoony style and "rainbow" theme.

http://www.mobygames.com/images/covers/l/19936-beamrider-atari-2600-front-cover.jpg

The Immortal

The Immortal (Genesis version)

Wasteland

Katamari Damacy

Discworld

Fallout

Metal Slug

Tomb Raider IV: The Last Revelation

Flashback

Time Commando

WarCraft II Tides of Darkness

Another World

Grand Theft Auto Vice City

Love the Wasteland one.

Also great is id Anthology box.

Nice thread!

My personal favorite is Carl Critchlow's cover art for Ečstatica. Version 1 and version 2.

Already posted before, but I prefer this cover for Wasteland. I think covers for Another World and Discworld are also great.

Some more excellent cover art both visually appealing and at the same time effective at hinting what kind of gaming experience you'll get:

SimCity 2000

Carmageddon

Ultima Underworld: The Stygian Abyss

Sam & Max: Hit the Road

Master of Orion II: Battle at Antares

Wow...

Talking about mandatory cover arts, this one must be included in this thread:

Art.

I'm surprised people forgot about it.

(no more links from me until the forum is fixed/rep abandoned, sorry)

Maybe the advent of digital publishers has robbed us of cover art as well. For many PC games, there aren’t even box covers any more. There’s some key art on the store front on Steam and GOG, and even GOG often struggles to find suitable artwork (famously for Tales of Monkey Island, they grabbed fan art by Laserschwert from the interwebs at first).

I’m a big fan of movie posters, and Drew Struzan in particular (also Richard Amsel and David Grove, to name just two). He made two covers for Indiana Jones games, the Emperor’s Tomb, neat but not spectacular, and The Infernal machine, which has a more free flowing, less horizontal composition and is a brilliant cover altogether.

However, William Eaken imitated Drew Struzan’s style for the Fate of Atlantis cover. And to this day I really love this poster!