Depends on what you mean by daunting. Do you mean because of their reputation in film history - Casablanca, Citizen Kane - or the difficulty of capturing the vision of a singular filmmaker - Last Year at Marienbad, 2001, 8 1/2? I think any successful movie would be daunting to remake. If the crew behind Skyfall and Spectre said they were going to remake Goldfinger next, that would be a pretty daunting task though there's certainly room for modern improvement.