It cannot be denied that Diablo 3 got mixed reviews, and substantial negative feedback post-release. See for example very low 3.8/10 Metacritic user rating (7864 Ratings), and average user rating of 2.2 / 5 on Amazon (3,116 customer reviews).
Comparatively Blizzard's Starcraft II: Wings of Liberty got 8.1 / 10 (2150 User Ratings). That means SC2 has (much) better lead designers who understand the franchise and fanbase.
Diablo 3 sold record amounts, yet many fans are seriously disappointed. Now there's new Action RPGs such as Path of Exile which many D3 fans prefer to play instead of D3.
Example: how can the low-budget Path of Exile be able to directly compete against Diablo 3? Diablo 3 is supposed to be the Triple A, blockbuster and gold-standard of the Action RPG genre! So something is amiss.
If budget isn't the cause, then it must be the faulty game design of the lead developers (repetitive gameplay, narrow restrictive level-design, no open world to explore, semi-cartoony washed out graphics, mediocre storyline etc).
Due to so much disappointment among fans it's questionable whether Diablo 4 and 5 would sell as well if Blizzard continues down the current game-design path.
I'm a big fan of the Diablo Franchise so I'm concerned about the disappointing state of Diablo 3.
Blizzard appears to be unaware of Diablo 3's downfall and severly overestimates itself. So they won't really listen to fans nor take essential measures to improve Diablo 3 and redeem the Diablo franchise.
Blizzard can pretend that Diablo 3 is the best Action RPG to date, but many fans think otherwise and will be reluctant to buy another Diablo game.
Update 1: here's a comparison of the Random Map Generator of Path of Exile VS Diablo 3:
Path of Exile's RMG is bigger, more complex, and has more replayability.
Diablo 3's is simplistic, smaller and fewer routes.
Update 2: After playing Path of Exile for a while. Here's my opinion thus far:
Path of Exile has a darker, more detailed and realistic graphics style. I think the lighting enhances the graphics of PoE a lot, and detailed textures greatly increases immersion.
Whereas Diablo 3's graphics are brighter, and unfortunately the textures are less detailed, more blurry. D3's lighting system is more basic too. Thus D3 doesn't feel as creepy or spooky as it should, and it doesn't draw the player in as much.
Winner: Path of Exile (Feb 2012)
Combat in PoE is slower, but feels like it has more weight to it, and thus its more satisfying when killing mobs. Diablo 3's combat is faster, but that makes it feel quite like a "meat grinder".
Winner: Undecided (Feb 2012)
I dislike PoE's more primitive semi-Barter system, lack of coins or gold. Because this makes trade for items more difficult when it requires a specific amount of X, Y or Z to get something. Coins, Money was invented for very useful reasons: e.g. to simplify trade between people, and allow easier storage of savings.
Winner: Diablo 3 (Feb 2012).
The Skill Tree of Path of Exile is Enormous, and confusing. I give props to D3 for ease of use. However, Path of Exile offers much more freedom and options to create very personalized and more unique characters.
Winner: Path of Exile (Feb 2012).
The Demise of Blizzard
The downfall of Diablo 3 could potentially be the turning point where Blizzard Entertainment itself enters its own demise, unless they change course.
I hope Blizzard can restore the Diablo Franchise to its former glory, but time will tell.
Edited by Hiderius, 16 February 2013 - 08:56 AM.