I think it is near impossible, to find an actor who is 'always in good films'. Even the greatest living actors like Robert De Niro (
Showtime, Hide and Seek) and Al Pacino (
Gigli, People I Know) have been in some very bad movies. However, i will still maintain that De Niro is, by quite a margin, the greatest living actor. His immersion into 'the method' allows him to become truly absorbed into a character. He can adopt a minimalistic approach, while still developing a characters' mental awareness in such a chilling way (
Taxi Driver, The King of Comedy). He can also portray a character with fervent intensity, the heralded Pacino-esque shout and spit technique, if you will (
Raging Bull).
Even looking back, acting greats like James Stewart
(Airport '77), Cary Grant
(None But The Lonely Heart) and Humphrey Bogart
(Tokyo Joe) have all been in some average films.Granted, these films are not unmitigated disasters but these actors didn't live back in the day when you could get paid $20 million for acting in unadulterated garbage like
Showtime and
Gigli.
The only actor i can think of that hasn't been in a bad film is the late John Cazale, who appeared in
The Godfather, The Godfather Part II, Dog Day Afternoon, The Deer Hunter and
The Conversation. There are three masterpieces (
The Godfather I & II, The Deer Hunter) and two very good films (
Dog Day Afternoon, The Conversation) in that filmography.