The 3rd edition of the D&D game marked a great shift in the rules of the game, but it also introduced a controversial Dungeonpunk aesthetic to the game's artwork.
All of a sudden, over-sized weapons became commonplace, armor started getting heavier, spikier, and more asymmetrical, and gratuitous buckles and straps were EVERYWHERE. All of a sudden elves had horribly mutated, uncanny-valley faces with giant, horrifically slanted eyes and ears that stuck out 6 inches from their heads. Halflings went from chubby little hobbits to toddler-sized humanoids with adult human proportions. Dwarves went from short stocky humanoids to midget linebackers with enormous feet. Even humans look more comic book-proportioned than realistic.
The artwork for 1st and 2nd ed AD&D, in contrast, had a very realistic, naturalistic look. Sure, the weapons and armor might have been a fancier than their historical counterparts, but in most cases, the equipment looked like it could really be used, and the people wearing it looked like they could actually be real people. Even the demi-humans had a certain plausibility to their design.
For a lot of folks (myself included), this dramatic shift in the tone of the artwork made the 3rd edition feel very cheesy and unrealistic. It felt more like the sort of thing you'd see in a video game or comic book, which undermined the verisimilitude of the imaginary worlds we were trying to create.
I'm not trying to be a grumpy old grognard for pointing this out, and it's not about being overly sensitive or picky. Like it or not, the artwork sets the tone for the game, and it it changes how people see the game in their imaginations.
Realistic artwork helps support the fantastic elements, giving them a plausible framework to contrast against. It's much easier to immerse yourself in a realistic gameworld. On the other hand, if the artwork sets a cartoony vision for that game, the players have to work that much harder to suspend their disbelief in the fantasy world.
3rd edition also marked a massive power increase for player characters, making them much more like superheroes within their world, rather than very lucky and/or skilled normal people, and I think this ties in with the same comic book/video game influence that I alluded to earlier.
I dislike the "Medieval Superhero" theme because it sets the PCs apart from the normal folk of their world and makes the NPCs seem like a hopelessly inferior species. I also think it's a lot more fun to work your way up from zero to hero rather than starting off as a certifiable badass. 3E and 4E have definately made it easier to advance which cheapens the experience, in my opinion.
But I digress. I don't want to stray too far into the rules, because this is about the artwork.
While I consider the 3E artwork to be a step backwards, the 4E artwork is just flat-out terrible. Everything that was bad about 3E artwork is multiplied tenfold in the 4E artwork. The artwork now clearly reflects an MMO influence and any sense of subtlety and realism is completely gone.
Sadly, while much of the artwork is actually very good from a technical perspective, and the production values are obviously better, there are very few illustrations that really grab me the way that a lot of those old-school drawings did (despite the amateurish nature of the artwork).
Dave LaForce's flooded dungeon picture above (from pg 68 of the 1E DMG) is a great example of how a rather crude drawing can still pack an emotional wallop.
This adventurer has just found himself stuck in a water trap, and while he's trying to get out a skeleton is sneaking up behind him. This picture preys on your primal fears (drowning, dark places, unseen enemies, a knife in the back) and hits you with a number of things all at once.
Notice too, that this doomed adventurer is wearing modest, realistic armor and equipment, and he's not built like Arnold Schwarzenegger... he's just some poor schmoe who's luck is probably about to run out. It's easy to relate to this guy and imagine yourself in his place.
Ideally what I'd like to see is artwork that had the soul of the old-school artwork with the technical ability of the new-school artwork. Too much of the new stuff just comes off as tasteless, trite, and derivative, while I end up finding myself drawn to the simple black and white artwork of the old-school for inspiration again and again.
I really do feel that the tone of the artwork is MUCH more important than WotC realizes, and that they're painting themselves in a corner with the current art direction.