I remember the graphics for both Diablo games as being slightly behind the times. At most barely on par with the norm at the time of release. Many complained that D2 should have been fully 3D... hence the update that came out to add a more 3D look to the game-world.
I actually hate to see how graphics have become the water-mark by which all games are judged before the game-play is even taken into account. Graphics are important but not that important.
Seems so many of today's gamers will avoid the best game created due to it's graphics being slightly less than the norm or old-school.
To me the game-play is king. Graphics are great when they add to the game-play but if they don't it doesn't ruin a game as long as it has well rounded game-play.
Take WoW for instance. I didn't care for the graphics at release but the game was fun so I stuck with it. I would have preferred it if they had stuck to the original darker gritty look from the preview videos release back in 2000 and 2001, before they went for that Saturday morning cartoon look.
Either way their graphics were good (some say great) but it was the game-play that keeps people playing and paying even today.