Which directors showed a ton of potential early in their career which they never really lived up to? Not that their more recent work is bad necessarily, just not what you'd hoped for.

Granted I can't knock them since they all are still making films, but, just not films I'm interested in...

Jim Wynorski, Fred Olen Ray, David DeCoteau are responsible for some of my favorite 80's/90's horror films/B-movies. All 3 are now pretty much just making made for TV Christmas movies.

Josh Becker, who is one of the longtime friends of Sam Raimi and Bruce Campbell, directed three very entertaining low budget movies: Thou Shalt Not Kill...Except, Lunatics: A Love Story, and Running Time (which was a technical accomplishment being shot in real time with very few cuts) ended up directing a really bad hokey made for Sci Fi Channel movie Alien Apocalypse, seemed he directed one other for Sci Fi, and a few TV shows.

Keith Gordon, most famous for playing Arnie in Christine (1983), I thought would become one of the bigger names in film directing after he made The Chocolate Wars, A Midnight Clear, Mother Night, but after a few more minor movies he's directing TV, again nothing against that, still, thought he'd be doing more film.