I think I have found a good way to point people towards quality Spaghetti Westerns in general.
Anything filmed before 1971, directed by the 3 Sergios (Leone, Corbucci and Sollima), Tonino Valerii, Antonino Margheriti, or Damiano Damiani, and/or starring LVC, Giuliano Gemma, Franco Nero and/or Tomas Milian is basically worth watching.
Anything directed by Gianfranco Parolini (with the exception of Tepepa) should be avoided (unless you like stupid/silly comedy SWs), but Enzo G. Castellari’s & Franco Nero’s works are worth watching beyond 1970, because “Kill them all and come back alone” is fun to watch and stars Frank Wolff, and “Keoma” because it would be a brilliant film if the soundtrack wasn’t the most gruesome atrocity ever to torture the viewer’s ears (maybe they should use it at Guantanamo Bay to get the t*****ists to confess instantly, but I guess that would be a crime against humanity). 
(Note that I consider any silly/comedic spaghetti westerns to be awful in general, including those filmed before 1971 - I’d make an exception for “Trinity is still my name” because it features some iconic scenes and has such a wholesome story that it’s even suitable to introduce children to the genre, and “Ace High” is watchable for starring the brilliant Eli Wallach).
Did I miss something? What’s your opinion?