Posting in a troll thread.
The only real way they're similar is that they've both been dumbed down considerably from their original concepts. Diablo 3 was designed to be played on consoles and tablets, so it is, by necessity, much simpler and baser than a typical PC RPG (see Path of Exile or, to a lesser extent, Kingdoms of Amalur.)
World of Warcraft has been bleeding subscribers and thus they're looking to pull in as many new markets (types of players) as possible.
Unfortunately for us PC gamers, we're left with games which lack polish (Path of Exile and KoA) or games that are designed to be played by 5 year olds (WoW and Diablo 3.) The third category would be games like Skyrim, which have potential but lack direction (which a lot of people like, and Skyrim was pretty fun for a while.) Or, games which shoehorn you in to a prescribed path (Dragon Age 2.) Really, the last go RPG for the PC was Dragon Age Origins. I was really hoping for Diablo 3 to be that, but it just isn't. Sure, it's story driven, but it's effectively a few cutscenes with a whole shitload of mindless clicking in between.
Mass Effect wasn't bad, but I don't consider it to really be an RPG. ME1 had some definite RPG elements to it, but ME2 was a cover-based shooter at its core. That's probably why I prefered ME1 overall to ME2. Haven't played ME3 yet...will wait until it's cheaper, but I've heard that it's a bit more RPGish than ME2, but not as much as ME1.
I'm not saying that PC RPGs should go all JRPG on us (like FF7, or whatever) but I wouldn't mind a bit more depth to my games...some focus on story and gameplay would be way awesome. It seems to me as though developers are trying to find ways to make their games more appealing to the general public (i.e. 10 year old boys) and in doing so, they're alienating their core audiance. That, unfortunately, is not limited to just PC games, though.