Yes and as usual, it's the fault of the casual gamer/mass market. Around the turn of the century the developers really started to downplay innovation and game length in favour of shorter games and better graphics in an effort to to appeal the casual fuckers.
In terms of business in theory it was a good move, in terms of game quality it was not. The end result was a massive boost to the rental and 2nd hand market because no-one in their right mind was going to spend £40 on a game they can finish in a weekend. Something the industry is still trying to crack down on and that will massively damage gaming. It's also why games like GTA sell so massively, because people know they'll actually get their moneys worth, but the lesser known games get buried.
There are so many reasons that you are incorrect that I am baffled. Gaming has been mass market for years, it's not been a niche market since you or I were kids. If you want to be "hardcore" go play a time-sink like WoW. Two major things have lead to the change in difficulty in games.
1) A maturing demographic: I got a NES when I was five years old for Christmas back in 1990. Back then even people who were teens during the first and second generation consoles were at most in their twenties. I am now closer to thirty than I'd like to admit and I still play games. I also have a job, a mortgage and significantly less time to play games than I did even five years ago. If games are shorter it gives me more time to enjoy more games. I'm far from alone on that, I would love, LOVE to have the time to play a game non-stop until a beat it. Hell sometimes I manage to find the time, but if I can't beat a game in a few weeks or it starts to lose my interest I put it on the shelf and leave it. Which is problematic because:
2) Story matters now. Look at the big ticket franchises. Beyond CoD, Halo and EA sports. You have Uncharted, Assassin's Creed, Batman, God of War. All of those games have story as a crucial element. Story telling in games is evolving rapidly, why would ANYONE buy a game for the story if they know the game itself is going to be a chore.
Finally "hardcore" gamers are irrelevant for a good reason. They tend to buy a game and play it to death before buying another game. I work as a tutor so I know from talking to my students about it that most of them buy two or three games a year, usually from the Fifa, CoD or whatever franchises. I would consider myself a hardcore gamer, but what happens when I beat a game? Do I go online so I can extend my e-peen?
No. I go to the store and buy a different game. Games that you can finish mean people buy more games. It's that simple. Those casual gamers you deride from your horse so high buy more games than hardcore users. If they didn't exist do you honestly think for a single goddamn second that games would have multi-million dollar budgets? Hell I would wager that over fifty, no seventy percent of world of warcrafts subscribers have never maxed out a character. Why? Because they're playing other games at the same time. And yet, it's the most successful game in History.
Also the question of whether games are getting easier or not is irrelevant because of the massive niche market developing in games that are more difficult than piercing your own cock (that seems appropriately difficult). Go play Demon's Souls and tell me then that games are too easy.
There's nothing worse than people who act like elitist pricks because they spent 200 hours grinding to tenth level prestige. Shit's not difficult, just time consuming.