This is also a tricky list because a LOT of the films I think of when I think of the 20s are actually from 1927-29. So, this list is as much (or more) things I need to see, as ones I can comment on.
And I actually may have seen the Merry Widow (1925) and Doctor Jack (1922) at the 1997 Silent Film fest, but I don't remember. I only remember Poor Little Rich Girl.
(Links to Hulu+, netflix, and youtube).
Notable Omissions: The Phantom Carriage, Way Down East, The Golem, Dr. Jekyll and Mr. Hyde, the Garage, the Last of the Mohicans
Notable omissions: Orphans of the Storm, The Kid
Um, I've got a blank here.
And I haven't actually SEEN Nosferatu, just Shadow of the Vampire, but... it seems well worth checking out? Other notable omissions: Dr. Mabuse: der Spieler, Doctor Jack, Robin Hood, Nanook of the North, Haxan
Ummm.... again. I got nothing. Things to be seen: Our Hospitality, The Hunchback of Notre Dame, Safety Last (how is that not online?!)
I love this one so much. The movie sequence is just so much fun and so clever.
The Navigator, The Last Laugh, Girl Shy, He Who Gets Slapped, the Sea Hawk, The Thief of Bagdad, Greed, Die Nibelungen: Siegfried and Kriemhild's Rache
Other options: The Merry Widow, Battleship Potemkin, The Phantom of the Opera, Stachka, The Wizard of Oz, The Lost World, Ben-Hur, The Big Parade, Seven Chances
Well worth checking out are Observations on Film Art's annual top 10 films... of the 20s. Here is 1922, here is 1921, and here is 1920.