The Dark Tower series cratered after Wizard and Glass. Couldn't even finish the 5th book, it was so bad, and I loved the first three.
Eyes of the Dragon (set in the Tower universe) was pretty cool. I still remember that one.
The Stand (book and miniseries) was OK. I kept expecting it to get awesome, but it never did.
Storm of the Century was great, one of the few things of his that didn't suck out loud on TV.
The Mist short story was great. Movie was OK until they changed the ending to be edgy.
That book about writing he did was boring as hell, but I finished it. Started Bag of Bones and dropped it. Those and book 5 of Dark Tower were his last works I tried.
Could care less about yet another go back and save Kennedy story. It's as tired as go back and kill Hitler. How about go back and save someone else? No one ever seems to go back and save MLK, for example.
I don't know that he's run out of ideas, so much as I just don't like what he's been coming up with over the last ten years.