I beat Fable 2. And then realized that no, it never did get better.
I actually "beat" Fallout 3. I didn't enjoy it. I found the atmosphere really creepy (bona-fide video game pansy here) and that sucked the fun out of it for me. I just did the main story as fast as I could. Any sidequests were happenstance.
Similarly, I only played BioShock to the Doctor. That game freaked the everliving shit out of me. I don't think that was a lot of total game percentage I went through, but it took me a long time because I creeped around, peeking around corners and then running away because I saw a shadow or someone whispered. I beat the doctor and then went into this one room where a dead body floated through a flooded hallway and I could see a shadow of someone hacking away at another body. As I went through the hallway, the lights went out and freaky music played and I crapped myself and turned the game off and sold it.