If D3 had not been billed as the sequel to D2, I think a lot of the hate would have been held back. Had they called it "World of Diablo" (or whatever), people may have realized that they were different types of game. For example, the skill system and crafting system in D3 are really neat ideas, but they aren't a logical successor to D2's mechanics.
Torchlight 2 on the other hand is the spiritual sequel to D2: it feels like D2. Personally, Matt Uelman's ambient background music makes a huge difference to me in the "feels like D1/D2" respect.
On a tangential note, I'm almost sad to say that Blizzard has pretty much killed all three of their franchises for me: WoW is boring and no Warcraft 3 sequel is in sight; SC2 single player campaigns are just there to subsidize the multiplayer (I'm not paying $60 again for one campaign); and now Diablo feels like WoW. Thankfully there will always be interesting new games and companies to supplant (or at least sidestep) the juggernauts.