Some are bad, but to me there are more boring or dull SWs, than poorly made I think.
The people at Cinecitta in Rome knew the trade of film-making I believe, but of course these were genre movies with low budgets, and not always enough creativity.
Most of the time the musical soundtracks are absolutely brilliant though, many times they are better than the films themselves
No one beats Leone when it comes to epic proportions I believe, but Corbucci's The Mercenary is fairly epic in size, even if it doesn't have the length of Leone's films.
Can't think of any more at the moment ???