I've just cracked into red dead redemption, which is actually pretty tame for an M rated game. (so far anyway, I'm pretty early in).
Not usually a big fan of western stuff, but I'd give it a thumbs up.
Also, the Mass Effect series is a must.
And Demon's Souls is good...you asked about spiking difficulty. It doesn't randomly spike in difficulty, it just spikes once at the beginning, then sits on top of the difficulty spike like it was a throne, and it points and laughs at you for the rest of the game.