Decades of cultivation eventually lead to fruition.

In other words, people have grown up with games making them more culturally acceptable, hardware prices have fallen dramatically making them more accessible for more people than ever before, and decades of game design have ironed out a lot of kinks that used to exist.

For a variety of reasons, motion pictures never really had these hurdles to overcome. If you had a camera, people and the ability to sync sound you were already most of the way there if you wanted to achieve something resembling modern cinematic storytelling, and film was never seen as being for children and nerds like gaming has been for so long. Film did have to build and refine its own language, but that was more or less finalized many decades before you or I were even born.

You were part of the lucrative demographic because you had an inherent interest in the form, the financial ability to actually take part in it, and the willingness to deal with its growing pains. For a developing form of entertainment that is extremely important, but as that form matures you can't expect it to rely on the obsessive hobbyists forever. As the barriers to entry were minimized or removed more people took part (this is not a bad thing), and publishers altered course accordingly.

And you can either accept that this is how the world works and be happy you got as much as you did and support the games that continue to aim for your interests, or you can complain that things are no longer revolving around you and attempt to paint that as some sort of failure on everyone else's part.

Expanding, in terms of more users playing games every day, different genres are being made to suit everybody's needs and tastes, and so on...

As for the second part, multiplayer game != e-sports game. One would know which game to pick for e-sports, as usually there is a lot of hype, press releases, interviews suggesting that the game will be e-sports compatible. :p

Yes it's not just restricted to the PC. There is a concerted effort from all publishers on all formats to chase the casual dollar and that has resulted in almost every game suffering some kind of streamlining. People point at Nintendo to blame but the real problem is developers have stopped listening to what their fans actually want in favor of focus groups. Usually they scoop up people at random who might not even play games and ask them what they want. It's a practice that has been brought into gaming from other industries and it's never worked there either. "How do we get people who don't drink coke to drink it? YES! New-COKE!".

Okay, I'm just going to ask:

Outside of RPGs (which have been trying to simplify their interfaces since their inception), what genres have been "streamlined"? I suppose FPS games have gun limits and regenerating shields, but that seems more like a step sideways than backwards to me since they manage to introduce their own complications.

Meanwhile, sports games have only gotten more complex, racing games are larger and have more options than ever before (on both the casual and the sim sides), strategy games go from Civilization Revolution on the simple side to Paradox titles and beyond on the complex side, platformers are now generally sold on their extreme difficulty (think Super Meat Boy and n+) despite originally being the casual games of their era, adventure games pretty much took the LucasArts route and stayed with it, space sims are copying Elite more than Wing Commander, and so on.

What actual, specific complaints are there? I can understand RPG fans being upset since party-based games have mostly fallen out of favor, but beyond that I'm struggling to see where this dumbing-down is actually occurring.

I agree. I just don't see most gaming genre becoming much more casual or easy than they used to be, with the occasional exception, but there have always been particularly easy and /or dumbed-down games.

What I mainly see is the creation of new genres to appeal to some new demographics of gamers. I also see the revival of puzzle games. That's not inherently bad, even if it diverts money from producing games I like to games I don't.

Of course, my main genre is RPGs so that particular dumbing down is painful for me. Even so, it's not as bad as people make it out to be. First, while DA 2 is horrible, DA O was the most old-school AAA game I've seen in years, and it wasn't that long ago. It's still possible that Bioware will learn from DA 2 and go back to what made DA O great.

Second, there's still the flourishing indie scene if big developers can't create anything worthwhile. I' for one, really enjoyed the Eschalon and Geneforge games. I can't wait to play Avadon. I'm very hopeful about Age of Decadence and Dead State.
I could go on.