...if you think Diablo 3 is a bad game you have become jaded about the passion of gaming...
Sorry to say this - I hate being outright dismissive - but no: if someone thinks Diablo III is a bad game, there isn't an excuse, reason or explanation that invalidates their opinion; to me, Diablo III is the perfect example of a 2 Star game.
I believe that Diablo III is a bad game because it is boring. It's the greatest sin a game can make, because all a game has to do is entertain. I can overlook the lacklustre art style, the insulting bad story, the horrendous DRM and all the horrible lag issues it creates, the complete removal of character customisation, and the absolute focus on the Auction House if the gameplay at it's core is terrific.
Unfortunately, Diablo III's gameplay is flat, slow and boring. Everything else - and I do mean everything else - is irrelevant to me; the game is not fun, and so it is a horribly bad game with a US$100,000,000.00 budget.
I give it 2 stars because it's pretty stable code and I feel bad crapping all over people's years of hard work.